[Reproducers] Support capturing a reproducer without an explicit path.

Tablegen doesn't support options that are both flags and take values as
an argument. I noticed this when doing the tablegen rewrite, but forgot
that that affected the reproducer --capture flag.

This patch makes --capture a flag and adds --capture-path to specify a
path for the reproducer. In reality I expect this to be mostly used for
testing, but it could be useful nonetheless.

Differential revision: https://reviews.llvm.org/D59238

llvm-svn: 355936

lldb/source/API/SBReproducer.cpp

@@ -2940,6 +2940,15 @@ SBRegistry::SBRegistry() {
   }
 }
 
+const char *SBReproducer::Capture() {
+  static std::string error;
+  if (auto e = Reproducer::Initialize(ReproducerMode::Capture, llvm::None)) {
+    error = llvm::toString(std::move(e));
+    return error.c_str();
+  }
+  return nullptr;
+}
+
 const char *SBReproducer::Capture(const char *path) {
   static std::string error;
   if (auto e =