Quick workaround for libSPIRV seemingly having became a stub in glslang-1.3.296

https://bugs.gentoo.org/941968

TODO?: rather than worry with the constant issues with glslang, should likely
always force shaderc -- it's also what upstream prefers by default and so the
glslang paths are hardly tested.
--- a/src/glsl/meson.build
+++ b/src/glsl/meson.build
@@ -39,4 +39,5 @@
 
     glslang_deps += spirv
+    glslang_deps += cxx.find_library('glslang', required: required, static: static)
 
     if static