contrib: add spirv-tools
spirv-opt provided by spirv-tools is used by Qt Shader Builder (qsb) for shader optimization.
Note that qsb expects spirv-opt
to be in a directory available in PATH
. spirv-tools
is built in native mode, this means that native contrib bin directory should be added to the path. This should be most likely a generic practice if it's not done already, and not limited to Qt.