Replace the sil-opt binary with a symlink to swift-frontend

rdar://76551283

Author: eeckstein

include/swift/Driver/Driver.h

@@ -166,6 +166,7 @@ class Driver {
   enum class DriverKind {
     Interactive,     // swift
     Batch,           // swiftc
+    SILOpt,          // sil-opt
     AutolinkExtract, // swift-autolink-extract
     SwiftIndent,     // swift-indent
     SymbolGraph,     // swift-symbolgraph

lib/Driver/Driver.cpp

@@ -99,6 +99,7 @@ void Driver::parseDriverKind(ArrayRef<const char *> Args) {
       llvm::StringSwitch<Optional<DriverKind>>(DriverName)
           .Case("swift", DriverKind::Interactive)
           .Case("swiftc", DriverKind::Batch)
+          .Case("sil-opt", DriverKind::SILOpt)
           .Case("swift-autolink-extract", DriverKind::AutolinkExtract)
           .Case("swift-indent", DriverKind::SwiftIndent)
           .Case("swift-symbolgraph-extract", DriverKind::SymbolGraph)
@@ -3555,6 +3556,7 @@ void Driver::printHelp(bool ShowHidden) const {
     ExcludedFlagsBitmask |= options::NoInteractiveOption;
     break;
   case DriverKind::Batch:
+  case DriverKind::SILOpt:
   case DriverKind::AutolinkExtract:
   case DriverKind::SwiftIndent:
   case DriverKind::SymbolGraph:

lib/DriverTool/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(driver_sources_and_options
                 driver.cpp
+                sil_opt_main.cpp
                 autolink_extract_main.cpp
                 modulewrap_main.cpp
                 swift_api_digester_main.cpp

lib/DriverTool/driver.cpp

@@ -63,6 +63,9 @@ std::string getExecutablePath(const char *FirstArg) {
   return llvm::sys::fs::getMainExecutable(FirstArg, P);
 }
 
+/// Run 'sil-opt'
+extern int sil_opt_main(ArrayRef<const char *> argv, void *MainAddr);
+
 /// Run 'swift-autolink-extract'.
 extern int autolink_extract_main(ArrayRef<const char *> Args, const char *Argv0,
                                  void *MainAddr);
@@ -281,6 +284,8 @@ static int run_driver(StringRef ExecName,
 
   Driver TheDriver(Path, ExecName, argv, Diags);
   switch (TheDriver.getDriverKind()) {
+  case Driver::DriverKind::SILOpt:
+    return sil_opt_main(argv, (void *)(intptr_t)getExecutablePath);
   case Driver::DriverKind::AutolinkExtract:
     return autolink_extract_main(
       TheDriver.getArgsWithoutProgramNameAndDriverMode(argv),