Separate exported includes out of flags

Exported includes have been maintained along with other C/C++ flags.
This makes dependencies unclear, and users have had to parse flags to
get exported directories. This separates exported includes and
exported flags, thus making data more structured and explicit.

Bug: 132818174
Test: m
Change-Id: I5c25ac2224988c4a67e4db6fd6e4d39090b74041

cc/sabi.go

@@ -28,8 +28,8 @@ var (
 )
 
 type SAbiProperties struct {
-	CreateSAbiDumps        bool `blueprint:"mutated"`
-	ReexportedIncludeFlags []string
+	CreateSAbiDumps    bool     `blueprint:"mutated"`
+	ReexportedIncludes []string `blueprint:"mutated"`
 }
 
 type sabi struct {