docs: Update documentation for GDC linker overriding

docs/markdown/snippets/ldc_linker_override.md

@@ -1,5 +1,7 @@
-## Support for overiding the linker with ldc
+## Support for overiding the linker with ldc and gdc
 
-LDC (the llvm D compiler) now honors D_LD linker variable (or d_ld in the cross
-file) and is able to pick differnt linkers. ld.bfd, ld.gold, ld.lld, ld64,
-link, and lld-link are currently supported.
+LDC (the llvm D compiler) and GDC (The Gnu D Compiler) now honor D_LD linker
+variable (or d_ld in the cross file) and is able to pick differnt linkers.
+
+GDC supports all of the same values as GCC, LDC supports ld.bfd, ld.gold,
+ld.lld, ld64, link, and lld-link.