diff -ur ruby-3.0.1/configure.ac ruby-3.0.1-patched/configure.ac
--- ruby-3.0.1/configure.ac	2021-04-05 05:33:42.000000000 -0700
+++ ruby-3.0.1-patched/configure.ac	2021-04-09 12:42:35.578174106 -0700
@@ -544,11 +544,16 @@
     rpathflag=`echo "$RPATHFLAG" | sed 's/%.*//'`
 ])
 
-RUBY_TRY_CFLAGS(-fdeclspec, [
-  RUBY_APPEND_OPTIONS(CC, -fdeclspec)
-  RUBY_APPEND_OPTIONS(MJIT_CC, -fdeclspec)
+RUBY_TRY_LDFLAGS(-fdeclspec, [fdeclspec=yes], [fdeclspec=no])
+AS_IF([test "$fdeclspec" = yes], [
+    RUBY_APPEND_OPTIONS(CFLAGS, -fdeclspec)
+    RUBY_APPEND_OPTIONS(cflags, -fdeclspec)
+    RUBY_APPEND_OPTIONS(orig_cflags, -fdeclspec)
+])
+RUBY_TRY_CXXFLAGS(-fdeclspec, [fdeclspec=yes], [fdeclspec=no])
+AS_IF([test "$fdeclspec" = yes], [
+    RUBY_APPEND_OPTIONS(CXXFLAGS, -fdeclspec)
 ])
-RUBY_TRY_CXXFLAGS(-fdeclspec, [RUBY_APPEND_OPTIONS(CXX, -fdeclspec)])
 
 AS_CASE([$RUBY_PATCHLEVEL], [-*],
 	[RUBY_DEVEL=yes], [RUBY_DEVEL=no])
@@ -1494,7 +1499,9 @@
 	AC_DEFINE_UNQUOTED([RUBY_ALIAS_FUNCTION_VOID(prot, name, args)],
 			   [RUBY_ALIAS_FUNCTION_TYPE(void, prot, name, args)])
     ])
+])
 
+{
     AC_CACHE_CHECK([for __atomic builtins], [rb_cv_gcc_atomic_builtins], [
 	AC_TRY_LINK([unsigned int atomic_var;],
 		    [
@@ -1525,7 +1532,6 @@
     AS_IF([test "$rb_cv_gcc_sync_builtins" = yes], [
 	AC_DEFINE(HAVE_GCC_SYNC_BUILTINS)
     ])
-])
 
     AC_CACHE_CHECK(for __builtin_unreachable, rb_cv_func___builtin_unreachable,
     [RUBY_WERROR_FLAG(
@@ -1538,6 +1544,7 @@
     AS_IF([test "$rb_cv_func___builtin_unreachable" = yes], [
 	AC_DEFINE_UNQUOTED(UNREACHABLE, [__builtin_unreachable()])
     ])
+}
 
 AC_CACHE_CHECK(for exported function attribute, rb_cv_func_exported, [
 rb_cv_func_exported=no
diff -ur ruby-3.0.1/template/Makefile.in ruby-3.0.1-patched/template/Makefile.in
--- ruby-3.0.1/template/Makefile.in	2021-04-05 05:33:42.000000000 -0700
+++ ruby-3.0.1-patched/template/Makefile.in	2021-04-09 12:42:35.579834751 -0700
@@ -75,7 +75,7 @@
 CC_VERSION = @CC_VERSION@
 OUTFLAG = @OUTFLAG@$(empty)
 COUTFLAG = @COUTFLAG@$(empty)
-CPPOUTFLAG = $(COUTFLAG)
+CPPOUTFLAG = >
 ARCH_FLAG = @ARCH_FLAG@
 CFLAGS_NO_ARCH = @CFLAGS@
 CFLAGS = $(CFLAGS_NO_ARCH) $(ARCH_FLAG)
diff -ur ruby-3.0.1/configure ruby-3.0.1-patched/configure
--- ruby-3.0.1/configure	2021-04-05 05:33:44.000000000 -0700
+++ ruby-3.0.1-patched/configure	2021-04-09 13:21:37.087380251 -0700
@@ -9345,8 +9345,10 @@
 fi
 
 
-    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether -fdeclspec is accepted as CFLAGS" >&5
-$as_echo_n "checking whether -fdeclspec is accepted as CFLAGS... " >&6; }
+    save_LDFLAGS="$LDFLAGS"
+    LDFLAGS="$LDFLAGS -fdeclspec"
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether -fdeclspec is accepted as LDFLAGS" >&5
+$as_echo_n "checking whether -fdeclspec is accepted as LDFLAGS... " >&6; }
     save_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS $rb_cv_warnflags"
 if test "${ac_c_werror_flag+set}"; then :
@@ -9360,7 +9362,6 @@
 fi
 ac_c_werror_flag=yes
 
-    CFLAGS="$CFLAGS -fdeclspec"
     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
@@ -9372,39 +9373,17 @@
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-
-  # RUBY_APPEND_OPTIONS(CC)
-	for rb_opt in -fdeclspec; do
-	case " ${CC-} " in #(
-  *" ${rb_opt} "*) :
-     ;; #(
-  '  ') :
-     CC="${rb_opt}" ;; #(
-  *) :
-     CC="$CC ${rb_opt}" ;;
-esac
-	done
-  # RUBY_APPEND_OPTIONS(MJIT_CC)
-	for rb_opt in -fdeclspec; do
-	case " ${MJIT_CC-} " in #(
-  *" ${rb_opt} "*) :
-     ;; #(
-  '  ') :
-     MJIT_CC="${rb_opt}" ;; #(
-  *) :
-     MJIT_CC="$MJIT_CC ${rb_opt}" ;;
-esac
-	done
-
+if ac_fn_c_try_link "$LINENO"; then :
+  fdeclspec=yes
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
     $as_echo "${msg_result_yes}yes${msg_reset}" >&6 ; }
 else
-
+  fdeclspec=no
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
     $as_echo "${msg_result_no}no${msg_reset}" >&6 ; }
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
 
 CFLAGS="$save_CFLAGS"
 save_CFLAGS=
@@ -9417,7 +9396,46 @@
   unset ac_c_werror_flag
 
 fi
+    LDFLAGS="$save_LDFLAGS"
+    save_LDFLAGS=
 
+if test "$fdeclspec" = yes; then :
+
+    # RUBY_APPEND_OPTIONS(CFLAGS)
+	for rb_opt in -fdeclspec; do
+	case " ${CFLAGS-} " in #(
+  *" ${rb_opt} "*) :
+     ;; #(
+  '  ') :
+     CFLAGS="${rb_opt}" ;; #(
+  *) :
+     CFLAGS="$CFLAGS ${rb_opt}" ;;
+esac
+	done
+    # RUBY_APPEND_OPTIONS(cflags)
+	for rb_opt in -fdeclspec; do
+	case " ${cflags-} " in #(
+  *" ${rb_opt} "*) :
+     ;; #(
+  '  ') :
+     cflags="${rb_opt}" ;; #(
+  *) :
+     cflags="$cflags ${rb_opt}" ;;
+esac
+	done
+    # RUBY_APPEND_OPTIONS(orig_cflags)
+	for rb_opt in -fdeclspec; do
+	case " ${orig_cflags-} " in #(
+  *" ${rb_opt} "*) :
+     ;; #(
+  '  ') :
+     orig_cflags="${rb_opt}" ;; #(
+  *) :
+     orig_cflags="$orig_cflags ${rb_opt}" ;;
+esac
+	done
+
+fi
 
 
     save_CXXFLAGS="$CXXFLAGS"
@@ -9455,21 +9473,11 @@
 }
 _ACEOF
 if ac_fn_cxx_try_link "$LINENO"; then :
-  # RUBY_APPEND_OPTIONS(CXX)
-	for rb_opt in -fdeclspec; do
-	case " ${CXX-} " in #(
-  *" ${rb_opt} "*) :
-     ;; #(
-  '  ') :
-     CXX="${rb_opt}" ;; #(
-  *) :
-     CXX="$CXX ${rb_opt}" ;;
-esac
-	done
+  fdeclspec=yes
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
     $as_echo "${msg_result_yes}yes${msg_reset}" >&6 ; }
 else
-
+  fdeclspec=no
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
     $as_echo "${msg_result_no}no${msg_reset}" >&6 ; }
 fi
@@ -9496,6 +9504,21 @@
     CXXFLAGS="$save_CXXFLAGS"
     save_CXXFLAGS=
 
+if test "$fdeclspec" = yes; then :
+
+    # RUBY_APPEND_OPTIONS(CXXFLAGS)
+	for rb_opt in -fdeclspec; do
+	case " ${CXXFLAGS-} " in #(
+  *" ${rb_opt} "*) :
+     ;; #(
+  '  ') :
+     CXXFLAGS="${rb_opt}" ;; #(
+  *) :
+     CXXFLAGS="$CXXFLAGS ${rb_opt}" ;;
+esac
+	done
+
+fi
 
 case $RUBY_PATCHLEVEL in #(
   -*) :
@@ -19369,6 +19392,9 @@
 
 fi
 
+fi
+
+{
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __atomic builtins" >&5
 $as_echo_n "checking for __atomic builtins... " >&6; }
 if ${rb_cv_gcc_atomic_builtins+:} false; then :
@@ -19450,8 +19476,6 @@
 
 fi
 
-fi
-
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_unreachable" >&5
 $as_echo_n "checking for __builtin_unreachable... " >&6; }
 if ${rb_cv_func___builtin_unreachable+:} false; then :
@@ -19511,6 +19535,7 @@
 
 
 fi
+}
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for exported function attribute" >&5
 $as_echo_n "checking for exported function attribute... " >&6; }