webkitgtk: Add musl patch from Alpine re:execinfo, use libc++ on ALLVM

pkgs/development/libraries/webkitgtk/2.4.nix

@@ -53,6 +53,8 @@ stdenv.mkDerivation rec {
     ./quartz-webcore.patch
     ./libc++.patch
     ./plugin-none.patch
+  ] ++ optionals stdenv.hostPlatform.isMusl [
+    ./fix-execinfo.patch
   ];
 
   configureFlags = with stdenv.lib; [

pkgs/development/libraries/webkitgtk/fix-execinfo.patch

@@ -0,0 +1,20 @@
+--- webkitgtk-2.2.0.orig/Source/WTF/wtf/Assertions.cpp
++++ webkitgtk-2.2.0/Source/WTF/wtf/Assertions.cpp
+@@ -64,7 +64,7 @@
+ #include <windows.h>
+ #endif
+ 
+-#if OS(DARWIN) || (OS(LINUX) && !defined(__UCLIBC__))
++#if OS(DARWIN) || (OS(LINUX) && defined(__GLIBC__) && !defined(__UCLIBC__))
+ #include <cxxabi.h>
+ #include <dlfcn.h>
+ #include <execinfo.h>
+@@ -242,7 +242,7 @@
+ 
+ void WTFGetBacktrace(void** stack, int* size)
+ {
+-#if OS(DARWIN) || (OS(LINUX) && !defined(__UCLIBC__))
++#if OS(DARWIN) || (OS(LINUX) && defined(__GLIBC__) && !defined(__UCLIBC__))
+     *size = backtrace(stack, *size);
+ #elif OS(WINDOWS) && !OS(WINCE)
+     // The CaptureStackBackTrace function is available in XP, but it is not defined