build: Update known-good files glslang commit ID

Change-Id: I5ef3ac82301d42cbdb616da4c995cf6dc53c6708
diff --git a/scripts/known_good.json b/scripts/known_good.json
index 705c06e..8148e43 100644
--- a/scripts/known_good.json
+++ b/scripts/known_good.json
@@ -6,7 +6,7 @@
       "sub_dir" : "glslang",
       "build_dir" : "glslang/build",
       "install_dir" : "glslang/build/install",
-      "commit" : "e06c7e9a515b716c731bda13f507546f107775d1",
+      "commit" : "21eebe74214488264bbf0d19323a03c13a9e53a7",
       "prebuild" : [
         "python update_glslang_sources.py"
       ]