wscript: switch shaderc checks to pkgconfig

Shaderc has been shipping .pc files for almost three years and we all
know of the advantages. If this turns out to be problematic the old checks
can be re-added but I'd like to avoid doing this preemptively.

wscript

@@ -680,14 +680,14 @@ video_output_features = [
         'desc': 'libshaderc SPIR-V compiler (shared library)',
         'deps': '!static-build',
         'groups': ['shaderc'],
-        'func': check_cc(header_name='shaderc/shaderc.h', lib='shaderc_shared'),
+        'func': check_pkg_config('shaderc'),
     }, {
         'name': 'shaderc-static',
         'desc': 'libshaderc SPIR-V compiler (static library)',
         'deps': '!shaderc-shared',
         'groups': ['shaderc'],
-        'func': check_cc(header_name='shaderc/shaderc.h',
-                         lib=['shaderc_combined', 'stdc++']),
+        'func': any_check(check_pkg_config('shaderc_combined'),
+                          check_pkg_config('shaderc_static')),
     }, {
         'name': '--shaderc',
         'desc': 'libshaderc SPIR-V compiler',