Print error messages when shader doesn't compile. (#2378)
Print error messages when shader doesn't compile. (#2378)

* Trace compile error if shader doesn't compile.

* remove redundant output

Co-authored-by: Lee Thomason <a5d98a0731a9b3d9f797434c264420da3ddc0c58@unity3d.com>
emoon/bgfx,emoon/bgfx,bkaradzic/bgfx,LWJGL-CI/bgfx,bkaradzic/bgfx,bkaradzic/bgfx,jdryg/bgfx,LWJGL-CI/bgfx,emoon/bgfx,LWJGL-CI/bgfx,LWJGL-CI/bgfx,jdryg/bgfx,jdryg/bgfx,bkaradzic/bgfx,jdryg/bgfx