Use CXXCOMPILE in gold/testsuite/Makefile for c++ testcases

I was playing with passing -std=c99 to an older version of gcc by
using CC="gcc-4 -std=c99", and ran into
cc1plus: error: command line option ‘-std=c99’ is valid for C/ObjC but
not for C++ [-Werror]
This obvious fix uses the correct compiler for a number of gold
testcases.

	* testsuite/Makefile.am (export_dynamic_plugin.o): Use CXXCOMPILE.
	(plugin_test_wrap_symbols_1.o): Likewise.
	(plugin_test_wrap_symbols_2.o): Likewise.
	* testsuite/Makefile.in: Regenerate.

gold/ChangeLog

@@ -1,3 +1,10 @@
+2020-06-16  Alan Modra  <amodra@gmail.com>
+
+	* testsuite/Makefile.am (export_dynamic_plugin.o): Use CXXCOMPILE.
+	(plugin_test_wrap_symbols_1.o): Likewise.
+	(plugin_test_wrap_symbols_2.o): Likewise.
+	* testsuite/Makefile.in: Regenerate.
+
 2020-06-15  Roland McGrath  <mcgrathr@google.com>
 
 	Implement -z start-stop-visibility=... option.

gold/testsuite/Makefile.am

@@ -2432,7 +2432,7 @@ MOSTLYCLEANFILES += plugin_test_12.err
 export_dynamic_plugin.o.syms: export_dynamic_plugin.o
 	$(TEST_READELF) -sW $< >$@ 2>/dev/null
 export_dynamic_plugin.o: export_dynamic_plugin.cc
-	$(COMPILE) -c -o $@ $<
+	$(CXXCOMPILE) -c -o $@ $<
 plugin_test_12: export_dynamic_plugin.o gcctestdir/ld plugin_test.so export_dynamic_plugin.o.syms
 	$(CXXLINK) -Wl,--no-demangle,--plugin,"./plugin_test.so",--plugin-opt,"_Z3foov" -Wl,--export-dynamic-symbol,"_Z3foov" export_dynamic_plugin.o.syms 2>plugin_test_12.err
 plugin_test_12.err: plugin_test_12
@@ -2443,9 +2443,9 @@ check_SCRIPTS += plugin_test_wrap_symbols.sh
 check_DATA += plugin_test_wrap_symbols.err
 MOSTLYCLEANFILES += plugin_test_wrap_symbols.err
 plugin_test_wrap_symbols_1.o: plugin_test_wrap_symbols_1.cc
-	$(COMPILE) -c -o $@ $<
+	$(CXXCOMPILE) -c -o $@ $<
 plugin_test_wrap_symbols_2.o: plugin_test_wrap_symbols_2.cc
-	$(COMPILE) -c -o $@ $<
+	$(CXXCOMPILE) -c -o $@ $<
 plugin_test_wrap_symbols: plugin_test_wrap_symbols_1.o plugin_test_wrap_symbols_2.o gcctestdir/ld plugin_test.so
 	$(CXXLINK) -Wl,--plugin,"./plugin_test.so" -Wl,--wrap=hello,--wrap=jello plugin_test_wrap_symbols_1.o plugin_test_wrap_symbols_2.o 2>plugin_test_wrap_symbols.err
 plugin_test_wrap_symbols.err: plugin_test_wrap_symbols

gold/testsuite/Makefile.in

@@ -9042,15 +9042,15 @@ uninstall-am:
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@export_dynamic_plugin.o.syms: export_dynamic_plugin.o
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(TEST_READELF) -sW $< >$@ 2>/dev/null
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@export_dynamic_plugin.o: export_dynamic_plugin.cc
-@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(COMPILE) -c -o $@ $<
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(CXXCOMPILE) -c -o $@ $<
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_test_12: export_dynamic_plugin.o gcctestdir/ld plugin_test.so export_dynamic_plugin.o.syms
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(CXXLINK) -Wl,--no-demangle,--plugin,"./plugin_test.so",--plugin-opt,"_Z3foov" -Wl,--export-dynamic-symbol,"_Z3foov" export_dynamic_plugin.o.syms 2>plugin_test_12.err
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_test_12.err: plugin_test_12
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	@touch plugin_test_12.err
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_test_wrap_symbols_1.o: plugin_test_wrap_symbols_1.cc
-@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(COMPILE) -c -o $@ $<
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(CXXCOMPILE) -c -o $@ $<
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_test_wrap_symbols_2.o: plugin_test_wrap_symbols_2.cc
-@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(COMPILE) -c -o $@ $<
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(CXXCOMPILE) -c -o $@ $<
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_test_wrap_symbols: plugin_test_wrap_symbols_1.o plugin_test_wrap_symbols_2.o gcctestdir/ld plugin_test.so
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(CXXLINK) -Wl,--plugin,"./plugin_test.so" -Wl,--wrap=hello,--wrap=jello plugin_test_wrap_symbols_1.o plugin_test_wrap_symbols_2.o 2>plugin_test_wrap_symbols.err
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_test_wrap_symbols.err: plugin_test_wrap_symbols