Remove POSIXLY_CORRECT from the build environment

Setting this will cause our invocation of ninja to fail. Even if we
fixed that, it's likely to run into other differences during the build.

Fixes: 112443729
Test: POSIXLY_CORRECT=1 m nothing
Change-Id: I0315955c9fd9536cc6cb0d7c700eed207f35cc80

ui/build/config.go

@@ -110,6 +110,7 @@ func NewConfig(ctx Context, args ...string) Config {
 		"DISPLAY",
 		"GREP_OPTIONS",
 		"NDK_ROOT",
+		"POSIXLY_CORRECT",
 
 		// Drop make flags
 		"MAKEFLAGS",