Stop using "-multiply_defined suppress" on macOS.

We started to use this linker switch in commit 9df308697 of
2004-07-13, which was in the OS X 10.3 era.  Apparently it's been a
no-op since around OS X 10.9.  Apple's most recent toolchain version
actively complains about it, so it's time to get rid of it.

Discussion: https://postgr.es/m/467042.1695766998@sss.pgh.pa.us

diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index 342496eecd04314f82e38a4bf04b7593fffa9744..e38333c27c2deed1aad35d32d5939846e2341b9b 100644 (file)
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -123,13 +123,13 @@ ifeq ($(PORTNAME), darwin)
     ifneq ($(SO_MAJOR_VERSION), 0)
       version_link     = -compatibility_version $(SO_MAJOR_VERSION) -current_version $(SO_MAJOR_VERSION).$(SO_MINOR_VERSION)
     endif
-    LINK.shared                = $(COMPILER) -dynamiclib -install_name '$(libdir)/lib$(NAME).$(SO_MAJOR_VERSION)$(DLSUFFIX)' $(version_link) $(exported_symbols_list) -multiply_defined suppress
+    LINK.shared                = $(COMPILER) -dynamiclib -install_name '$(libdir)/lib$(NAME).$(SO_MAJOR_VERSION)$(DLSUFFIX)' $(version_link) $(exported_symbols_list)
     shlib              = lib$(NAME).$(SO_MAJOR_VERSION).$(SO_MINOR_VERSION)$(DLSUFFIX)
     shlib_major                = lib$(NAME).$(SO_MAJOR_VERSION)$(DLSUFFIX)
   else
     # loadable module
     DLSUFFIX           = .so
-    LINK.shared                = $(COMPILER) -bundle -multiply_defined suppress
+    LINK.shared                = $(COMPILER) -bundle
   endif
   BUILD.exports                = $(AWK) '/^[^\#]/ {printf "_%s\n",$$1}' $< >$@
   exports_file         = $(SHLIB_EXPORTS:%.txt=%.list)