Consolidate global cflags

Move all the flags that are used everywhere (or should be used
everywhere) into cc/config/global.go:
-no-canonical-prefixes
-fno-exceptions
-Wno-multichar
-O2
-g
-fno-strict-aliasing

Also remove flags that are already in noOverrideGlobalCflags:
-Werror=pointer-to-int-cast
-Werror=int-to-pointer-cast

x86 and x86_64 were specifying -fstrict-aliasing, but that was
being overriden later by -fno-strict-aliasing, so remove it.
ARM devices still override -fno-strict-aliasing to -fstrict-aliasing
when using ARM (vs. Thumb) instruction set.

Bug: 68855788
Test: m checkbuild
Change-Id: Ia2b5891bdefb60f974ad92b4b84a8548c2dcc7dc

cc/config/x86_linux_host.go

@@ -22,15 +22,11 @@ import (
 
 var (
 	linuxCflags = []string{
-		"-fno-exceptions", // from build/core/combo/select.mk
-		"-Wno-multichar",  // from build/core/combo/select.mk
-
 		"-fdiagnostics-color",
 
 		"-Wa,--noexecstack",
 
 		"-fPIC",
-		"-no-canonical-prefixes",
 
 		"-U_FORTIFY_SOURCE",
 		"-D_FORTIFY_SOURCE=2",
@@ -40,11 +36,6 @@ var (
 		//See bug 12708004.
 		"-D__STDC_FORMAT_MACROS",
 		"-D__STDC_CONSTANT_MACROS",
-
-		// HOST_RELEASE_CFLAGS
-		"-O2", // from build/core/combo/select.mk
-		"-g",  // from build/core/combo/select.mk
-		"-fno-strict-aliasing", // from build/core/combo/select.mk
 	}
 
 	linuxLdflags = []string{