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