Pass javac flags to errorprone builds

Pass CommonJdkFlags to errorprone builds, which is required for
frameworks/base/layoutlib/create to work correctly.  Unfortunately,
javac and errorprone cannot use the same syntax for the heap size,
javac needs -J-Xmx and errorprone needs -Xmx, so split the heap size
flag out into a separate variable.

Test: m -j RUN_ERROR_PRONE=true javac-check
Change-Id: Icd7f8cf627534fb089ec83e462c060572dd2d20c
diff --git a/java/config/config.go b/java/config/config.go
index 90d0fb5..c6c8fff 100644
--- a/java/config/config.go
+++ b/java/config/config.go
@@ -26,14 +26,17 @@
 var (
 	pctx = android.NewPackageContext("android/soong/java/config")
 
+	JavacHeapSize = "2048M"
+
 	DefaultLibraries = []string{"core-oj", "core-libart", "ext", "framework", "okhttp"}
 )
 
 func init() {
 	pctx.Import("github.com/google/blueprint/bootstrap")
 
+	pctx.StaticVariable("JavacHeapFlags", "-J-Xmx"+JavacHeapSize)
+
 	pctx.StaticVariable("CommonJdkFlags", strings.Join([]string{
-		`-J-Xmx2048M`,
 		`-Xmaxerrs 9999999`,
 		`-encoding UTF-8`,
 		`-sourcepath ""`,