Setup dependent external sources

Setup dependent external sources

This patch includes below 3 patches. With these patches, it sets up
dependent external sources required for building VK-GL-CTS.

============ Patch 1 ============
Getting external sources for build

Fetching sources and modify for TIZEN.
.gitignore is deleted because gbs can't export sources with it.

Change-Id: I6c5862baf1ddba9648e23319c60d903d6f279ab9
Signed-off-by: Hoyub Lee <hoyub.lee@samsung.com>
============ Patch 2 ============
Apply git commits of external sources

glslang, spirv-headers and spirv-tools have each own git on their
directories. Each git has committed changes, so this has made diff on
VK-GL-CTS git.

Change-Id: I0ad161b3c2c6056f3d0ec174a78bd8c7fa6a5a78
Signed-off-by: Hoyub Lee <hoyub.lee@samsung.com>
============ Patch 3 ============
Add glslang, spirv-tools and spirv-headers

1. Fetch source code by fetch_sources.py;
2. Remove .git files;
3. Add necessary build requirements.

Change-Id: Ib1af29b1d62935634fbc604824345f99f8b4fa37
Signed-off-by:Xuelian Bai<xuelian.bai@samsung.com>

Change-Id: I8965206bc3e1ebd575d4b9e5b66887bf41d8e5ad
Signed-off-by: Hoyub Lee <hoyub.lee@samsung.com>