scons: Pass -fno-strict-aliasing to gcc.

Strict aliasing tule violations were fixed on master, but
they're still causing problem in this branch, so disable this assumptions.

Do not apply this fix to master (revert when you merge).

scons/gallium.py

@@ -370,6 +370,7 @@ def generate(env):
             '-Wno-long-long',
             '-ffast-math',
             '-fmessage-length=0', # be nice to Eclipse
+            '-fno-strict-aliasing', # we violate strict pointer aliasing rules
         ]
         cflags += [
             '-Werror=declaration-after-statement',