qtwebkit: unbreak with clang 11 on powerpc

Disable some code assuming that 8 byte __sync_* operators are not
available on that arch and as such trying to redefine builtin functions.

OK jca@, gkoehler@ and rsadowski@ (maintainer)

x11/qt5/qtwebkit/Makefile

@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile,v 1.31 2021/05/08 14:58:43 sthen Exp $
+# $OpenBSD: Makefile,v 1.32 2021/05/11 15:33:59 cwen Exp $
 
 COMMENT =		QtWebKit with a more modern WebKit code base
 
@@ -15,7 +15,7 @@ PKGNAME =		qtwebkit-${VERSION}
 PKGSPEC =		qtwebkit->=${VERSION}v0
 
 EPOCH =			0
-REVISION =		3
+REVISION =		4
 
 
 SHARED_LIBS +=  Qt5WebKit               3.1 # 5.9

x11/qt5/qtwebkit/patches/patch-Source_WTF_wtf_Atomics_cpp

@@ -0,0 +1,17 @@
+$OpenBSD: patch-Source_WTF_wtf_Atomics_cpp,v 1.1 2021/05/11 15:33:59 cwen Exp $
+
+powerpc fix: don't redefine 64-bits __sync_* built-ins operators
+
+Index: Source/WTF/wtf/Atomics.cpp
+--- Source/WTF/wtf/Atomics.cpp.orig
++++ Source/WTF/wtf/Atomics.cpp
+@@ -32,7 +32,8 @@
+ // (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56296). GCC >= 4.8 will support __atomic_* builtin
+ // functions for this purpose for all the GCC targets, but for current compilers we have to include
+ // our own implementation.
+-#if COMPILER(GCC_OR_CLANG) && !defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8) && USE(PTHREADS)
++#if !defined(__powerpc__) \
++    && COMPILER(GCC_OR_CLANG) && !defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8) && USE(PTHREADS)
+ 
+ #include "ThreadingPrimitives.h"
+