The parameter linkedShaderStages is passed to
GlslangGetShaderSpirvCode(), but is unused. This CL uses the parameter,
rather than gl::AllShaderTypes().

This CL also removes the unused parameter variableInfoMap from the call
chain.

Bug: angleproject:3570
Change-Id: Ic60084e87cb2aa2a245e3e963598851331379e89
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2412364
Commit-Queue: Tim Van Patten <timvp@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>