[libTooling] Recognize sccache as a compiler wrapper in compilation database commands

[nridge]

Summary

sccache is a compiler caching tool similar to ccache.

[nridge]

Link to sccache for reference: https://github.com/mozilla/sccache/

[nridge]

Review ping :)

[sammccall]

Thanks! Sorry about missing this...

clang/lib/Tooling/JSONCompilationDatabase.cpp

 // compiler as an argument, e.g. distcc gcc -O3 foo.c.
 // These end up in compile_commands.json when people set CC="distcc gcc".
 // Clang's driver doesn't understand this, so we need to unwrap.
 static bool unwrapCommand(std::vector<std::string> &Args) {
   if (Args.size() < 2)
     return false;
   StringRef Wrapper =
       stripExecutableExtension(llvm::sys::path::filename(Args.front()));
-  if (Wrapper == "distcc" || Wrapper == "gomacc" || Wrapper == "ccache") {
+  if (Wrapper == "distcc" || Wrapper == "gomacc" || Wrapper == "ccache" ||
+      Wrapper == "sccache") {
     // Most of these wrappers support being invoked 3 ways:
     // `distcc g++ file.c` This is the mode we're trying to match.
     //                     We need to drop `distcc`.
     // `distcc file.c`     This acts like compiler is cc or similar.
     //                     Clang's driver can handle this, no change needed.
     // `g++ file.c`        g++ is a symlink to distcc.
     //                     We don't even notice this case, and all is well.
     //

clang/unittests/Tooling/CompilationDatabaseTest.cpp

TEST(findCompileArgsInJsonDatabase, FindsEntry) {
   ASSERT_EQ(1u, FoundCommand.CommandLine.size()) << ErrorMessage;
   EXPECT_EQ("command4", FoundCommand.CommandLine[0]) << ErrorMessage;
 }
 
 TEST(findCompileArgsInJsonDatabase, ParsesCompilerWrappers) {
   std::vector<std::pair<std::string, std::string>> Cases = {
       {"distcc gcc foo.c", "gcc foo.c"},
       {"gomacc clang++ foo.c", "clang++ foo.c"},
+      {"sccache clang++ foo.c", "clang++ foo.c"},
       {"ccache gcc foo.c", "gcc foo.c"},
       {"ccache.exe gcc foo.c", "gcc foo.c"},
       {"ccache g++.exe foo.c", "g++.exe foo.c"},
       {"ccache distcc gcc foo.c", "gcc foo.c"},
 
       {"distcc foo.c", "distcc foo.c"},
       {"distcc -I/foo/bar foo.c", "distcc -I/foo/bar foo.c"},
   };