llvm: add forgotten patch, WIP

pkgs/development/compilers/llvm/set_soname.patch

@@ -0,0 +1,12 @@
+https://bugs.gentoo.org/show_bug.cgi?id=409267
+http://llvm.org/bugs/show_bug.cgi?id=12334
+--- tools/llvm-shlib/Makefile.orig	2012-03-26 18:14:13.071797115 +0200
++++ tools/llvm-shlib/Makefile	2012-03-26 17:31:12.491196254 +0200
+@@ -67,6 +67,7 @@
+     # Include everything from the .a's into the shared library.
+     LLVMLibsOptions := -Wl,--whole-archive $(LLVMLibsOptions) \
+                        -Wl,--no-whole-archive
++    LLVMLibsOptions += -Wl,--soname,lib$(LIBRARYNAME)$(SHLIBEXT)
+ endif
+ 
+ ifeq ($(HOST_OS),Linux)