Move toolchain and global variables into separate package

Move all of the configuration into a cc/config package

Change-Id: If56fc7242062ed1ce3cb297f78a1e0ef7537373c
diff --git a/cc/check.go b/cc/check.go
index f4b2834..82d5a9f 100644
--- a/cc/check.go
+++ b/cc/check.go
@@ -20,6 +20,8 @@
 import (
 	"path/filepath"
 	"strings"
+
+	"android/soong/cc/config"
 )
 
 // Check for invalid c/conly/cpp/asflags and suggest alternatives. Only use this
@@ -32,7 +34,7 @@
 			ctx.PropertyErrorf(prop, "Flag `%s` must start with `-`", flag)
 		} else if strings.HasPrefix(flag, "-I") || strings.HasPrefix(flag, "-isystem") {
 			ctx.PropertyErrorf(prop, "Bad flag `%s`, use local_include_dirs or include_dirs instead", flag)
-		} else if inList(flag, illegalFlags) {
+		} else if inList(flag, config.IllegalFlags) {
 			ctx.PropertyErrorf(prop, "Illegal flag `%s`", flag)
 		} else if strings.Contains(flag, " ") {
 			args := strings.Split(flag, " ")