Fix build scripts.

kokoro/macos-clang-release-bazel/build.sh

@@ -25,6 +25,8 @@ CXX=clang++
 SRC=$PWD/github/glslang
 cd $SRC
 
+mv External third_party
+
 # Get bazel 0.29.1.
 gsutil cp gs://bazel/0.29.1/release/bazel-0.29.1-darwin-x86_64 .
 chmod +x bazel-0.29.1-darwin-x86_64

kokoro/windows-msvc-2015-release-bazel/build.bat

@@ -22,6 +22,8 @@ set SRC=%cd%\github\glslang
 set PATH=C:\python36;%PATH%
 cd %SRC%
 
+mv External third_party
+
 :: REM Install Bazel.
 wget -q https://github.com/bazelbuild/bazel/releases/download/0.29.1/bazel-0.29.1-windows-x86_64.zip
 unzip -q bazel-0.29.1-windows-x86_64.zip