Toolchain+Ports: Split the GCC patches

This shouldn't cause any breaking changes, so a toolchain rebuild is not
required.

As per Hendiadyoin's request, math errno is disabled by default, which
should enable some extra compiler optimizations in LibGL and LibSoftGPU
code that uses math functions heavily.

Co-Authored-By: Ali Mohammad Pur <mpfard@serenityos.org>

Toolchain/Patches/gcc/0002-fixincludes-Skip-for-SerenityOS-targets.patch

@@ -0,0 +1,29 @@
+From e7d65e2c0943078214d9231cbb5c5e8eb9b5c726 Mon Sep 17 00:00:00 2001
+From: Andreas Kling <awesomekling@gmail.com>
+Date: Fri, 5 Apr 2019 03:02:52 +0200
+Subject: [PATCH 2/6] fixincludes: Skip for SerenityOS targets
+
+`fixincludes` is responsible for fixing mistakes in system headers that
+rely in compiler extensions that GCC doesn't support or cause errors in
+C++ mode.
+
+Our headers don't have such problems, so this hack is of no use for us.
+---
+ fixincludes/mkfixinc.sh | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/fixincludes/mkfixinc.sh b/fixincludes/mkfixinc.sh
+index df90720b7..a45cdd0de 100755
+--- a/fixincludes/mkfixinc.sh
++++ b/fixincludes/mkfixinc.sh
+@@ -11,6 +11,7 @@ target=fixinc.sh
+ 
+ # Check for special fix rules for particular targets
+ case $machine in
++    *-serenity* | \
+     i?86-*-cygwin* | \
+     i?86-*-mingw32* | \
+     x86_64-*-mingw32* | \
+-- 
+2.36.1
+