Use -Bsymbolic-functions instead of -Bsymbolic

Epoxy updates the function pointers in order to avoid calling the
resolver multiple times, but with -Bsymbolic we're going to update the
copy inside libepoxy, instead of the relocated copy in the code using
libepoxy. This leads to libepoxy constantly querying the function
resolver code instead of just once.

We still want to avoid intra-library relocations for our functions,
but we need to live with them for our global function pointers.

See issue #171

src/Makefile.am

@@ -116,7 +116,7 @@ libepoxy_la_SOURCES = \
 
 libepoxy_la_LDFLAGS = \
 	-no-undefined \
-        -Bsymbolic \
+        -Bsymbolic-functions \
 	$()
 
 libepoxy_la_LIBADD = \

src/meson.build

@@ -51,9 +51,9 @@ common_ldflags = []
 
 if host_system == 'linux' and cc.get_id() == 'gcc'
   if meson.version().version_compare('>= 0.46.0')
-    common_ldflags += cc.get_supported_link_arguments([ '-Wl,-Bsymbolic', '-Wl,-z,relro' ])
+    common_ldflags += cc.get_supported_link_arguments([ '-Wl,-Bsymbolic-functions', '-Wl,-z,relro' ])
   else
-    common_ldflags += [ '-Wl,-Bsymbolic', '-Wl,-z,relro', ]
+    common_ldflags += [ '-Wl,-Bsymbolic-functions', '-Wl,-z,relro', ]
   endif
 endif