Add sccache support.

mesonbuild/compilers/detect.py

diff --git a/mesonbuild/compilers/detect.py b/mesonbuild/compilers/detect.py
index 5e0710b..ffb0063 100644
--- a/mesonbuild/compilers/detect.py
+++ b/mesonbuild/compilers/detect.py
@@ -554,8 +554,13 @@
                 raise EnvironmentException(m)
             cls = VisualStudioCCompiler if lang == 'c' else VisualStudioCPPCompiler
             linker = guess_win_linker(env, ['link'], cls, for_machine)
+            # As of this writing, CCache does not support MSVC but sccache does.
+            if 'sccache' in ccache:
+                final_compiler = ccache + compiler
+            else:
+                final_compiler = compiler
             return cls(
-                compiler, version, for_machine, is_cross, info, target,
+                final_compiler, version, for_machine, is_cross, info, target,
                 exe_wrap, full_version=cl_signature, linker=linker)
         if 'PGI Compilers' in out:
             cls = PGICCompiler if lang == 'c' else PGICPPCompiler

mesonbuild/envconfig.py

diff --git a/mesonbuild/envconfig.py b/mesonbuild/envconfig.py
index 307aac3..2a112df 100644
--- a/mesonbuild/envconfig.py
+++ b/mesonbuild/envconfig.py
@@ -385,6 +385,14 @@
             return []
         return ['ccache']
 
+    @staticmethod
+    def detect_sccache() -> T.List[str]:
+        try:
+            subprocess.check_call(['sccache', '--version'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        except (OSError, subprocess.CalledProcessError):
+            return []
+        return ['sccache']
+
     @classmethod
     def parse_entry(cls, entry: T.Union[str, T.List[str]]) -> T.Tuple[T.List[str], T.List[str]]:
         compiler = mesonlib.stringlistify(entry)
@@ -392,6 +400,9 @@
         if compiler[0] == 'ccache':
             compiler = compiler[1:]
             ccache = cls.detect_ccache()
+        elif compiler[0] == 'sccache':
+            compiler = compiler[1:]
+            ccache = cls.detect_sccache()
         else:
             ccache = []
         # Return value has to be a list of compiler 'choices'