meson: Always use -fno-strict-aliasing and -fno-strict-overflow

SPA does not respect the C strict aliasing rules at all, so any code
that uses it must be built with -fno-strict-aliasing.  Furthermore,
there is code in SPA that compares pointers that point to different
objects, so -fno-strict-overflow is also needed.

meson.build

@@ -81,6 +81,7 @@ pkgconfig = import('pkgconfig')
 common_flags = [
   '-fvisibility=hidden',
   '-fno-strict-aliasing',
+  '-fno-strict-overflow',
   '-Werror=suggest-attribute=format',
   '-Wsign-compare',
   '-Wpointer-arith',