Prevent stripping on Gentoo

Patch by Ryan Fox

--- a/Makefile.mk
+++ b/Makefile.mk
@@ -24,7 +24,7 @@ ifeq ($(MACOS),true)
 LINK_OPTS  = -Wl,-dead_strip -Wl,-dead_strip_dylibs
 else
 # Common linker flags
-LINK_OPTS  = -Wl,-O1 -Wl,--as-needed -Wl,--strip-all
+LINK_OPTS  = -Wl,-O1 -Wl,--as-needed
 endif
 
 ifneq ($(WIN32),true)