libgo: fix go_export extraction on Darwin

    
    On Darwin, the section name is prefixed with the segment name, __GNU_GO.
    
    Reviewed-on: https://go-review.googlesource.com/c/151097

From-SVN: r269271

gcc/go/gofrontend/MERGE

-74533ed435a1a77e6f9ec8f6cf5db1695c2568e8
+08f1c400ec95d70a5cf5a08b1600fa5445e42361
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/Makefile.am

@@ -13,6 +13,12 @@ if LIBGO_IS_RTEMS
 subdirs = testsuite
 endif
 
+if LIBGO_IS_DARWIN
+GO_EXPORT_SECTION_NAME = __GNU_GO.__go_export
+else
+GO_EXPORT_SECTION_NAME = .go_export
+endif
+
 SUBDIRS = ${subdirs}
 
 gcc_version := $(shell $(GOC) -dumpversion)
@@ -818,7 +824,7 @@ BUILDGOX = \
 	if test ! -f $$f; then \
 	  f="$(basename $(<D)/.libs/$(<F)).o"; \
 	fi; \
-	$(OBJCOPY) -j .go_export $$f $@.tmp; \
+	$(OBJCOPY) -j $(GO_EXPORT_SECTION_NAME) $$f $@.tmp; \
 	$(SHELL) $(srcdir)/mvifdiff.sh $@.tmp `echo $@ | sed -e 's/s-gox/gox/'`
 
 GOTESTFLAGS =

libgo/Makefile.in

@@ -529,6 +529,8 @@ top_srcdir = @top_srcdir@
 # Go support.
 SUFFIXES = .c .go .gox .o .obj .lo .a
 @LIBGO_IS_RTEMS_TRUE@subdirs = testsuite
+@LIBGO_IS_DARWIN_FALSE@GO_EXPORT_SECTION_NAME = .go_export
+@LIBGO_IS_DARWIN_TRUE@GO_EXPORT_SECTION_NAME = __GNU_GO.__go_export
 SUBDIRS = ${subdirs}
 gcc_version := $(shell $(GOC) -dumpversion)
 MAINT_CHARSET = latin1
@@ -1001,7 +1003,7 @@ BUILDGOX = \
 	if test ! -f $$f; then \
 	  f="$(basename $(<D)/.libs/$(<F)).o"; \
 	fi; \
-	$(OBJCOPY) -j .go_export $$f $@.tmp; \
+	$(OBJCOPY) -j $(GO_EXPORT_SECTION_NAME) $$f $@.tmp; \
 	$(SHELL) $(srcdir)/mvifdiff.sh $@.tmp `echo $@ | sed -e 's/s-gox/gox/'`
 
 GOTESTFLAGS =