Fixup unused parameter warnings

This CL removes the current parameters which are unused in order to
fixup the issued clang warnings.

BUILD.gn: remove the static_library target.

This had no sources and depended on a source_set which is an invalid use
of GN because the source_set gets propagated to dependents of the
static_library instead.

Fix a parse issue of imageAtomicCompSwap()

The max count of arguments is 5 when image2DMS/image2DMSArray is
specified.

Fix flags.nonprivate to be true for workgroup memory, which is implicitly workgroupcoherent/nonprivate

Fix flags.nonprivate to be true for workgroup memory, which is implicitly workgroupcoherent/nonprivate

Allow redeclaration of builtin interface blocks in mesh shader

Fix inferred output primitive for GL_NV_geometry_shader_passthrough 

For GL_NV_geometry_shader_passthrough extension, the Inferred output primitive for ElgTriangles should be ElgTriangleStrip.

Also removed unnecessary relax for GL_NV_geometry_shader_passthrough in link validate

Enhancement: add extra command line options that modifies aml

Apart from allowing redeclaration of gl_MeshPerVertexNV and gl_MeshPerPrimitiveNV blocks, this change also -
- Resize clip/cull perview distances based on static index use
- Error out use of both single-view and per-view builtins
- Add new gtests with redeclared blocks and edit existing test output
- Fix couple of typos

BUILD.gn: glslang_sources need the public config too

BUILD.gn: only use complete_static_lib on mac

This will be used to generate uniform locations with --aml

Add ES 320 support and additional error checks for SPV_NV_mesh_shader

Also continue error checking post requireStage() check

BUILD.gn: make the static_lib complete to fix the build on OSX

This also fixes some cpp files that uncover issues when building
with the flags turned off.

Remove NV_EXTENSION ifdefs from ShaderLang.h

This allows library consumers to work without have to set
NV_EXTENSIONS.

Fix missing case label for miss stage.

Add BUILD.gn configuration.

- Add ES 320 support
- Error out use of perprimitiveNV for non mesh/fragment shaders
- Error out use of mesh/task shaders w/o use of NV_mesh_shader
- Error out use of NV_mesh_shader for non task/mesh shaders
- Error out use of perviewNV for non mesh shaders
- Error out use of taskNV for non mesh/task shaders
- Add test case for mesh shader with ES 320 profile

This CL adds the necessary configuration to build glslang inside a
Chromium checkout. Two build warnings were fixed in the process to
make things compile.