[lld][WebAssembly] Add support for LLD_REPRODUCE

[sbc100]

Summary

This is feature of the ELF and COFF linker that we were missing until
now.

lld/test/wasm/reproduce.ll

-; REQUIRES: shell
-; RUN: rm -rf %t.dir
-; RUN: mkdir -p %t.dir
-; RUN: llc -filetype=obj %s -o %t.dir/foo.o
-; RUN: wasm-ld --reproduce=%t.dir/repro.tar -o %t.dir/out.wasm %t.dir/foo.o
-
-; RUN: cd %t.dir
-; RUN: tar tf repro.tar | FileCheck --check-prefix=TAR %s
-
-; TAR: repro/response.txt
-; TAR: repro/version.txt
-; TAR: repro/{{.*}}/foo.o
-
-; RUN: tar xf repro.tar
-; RUN: FileCheck --check-prefix=RSP %s < repro/response.txt
-
-; RSP: -o {{.*}}out.wasm
-; RSP: {{.*}}/foo.o
-
-; RUN: FileCheck %s --check-prefix=VERSION < repro/version.txt
-; VERSION: LLD
-
-target triple = "wasm32-unknown-unknown"
-
-define void @_start() {
-  ret void
-}

lld/test/wasm/reproduce.s

+# REQUIRES: shell
+# RUN: rm -rf %t.dir
+# RUN: mkdir -p %t.dir
+# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.dir/foo.o %s
+# RUN: wasm-ld --reproduce=%t.dir/repro.tar -o %t.dir/out.wasm %t.dir/foo.o
+# RUN: env LLD_REPRODUCE=%t.dir/repro2.tar wasm-ld -o %t.dir/out.wasm %t.dir/foo.o
+
+# RUN: cd %t.dir
+# RUN: tar tf repro.tar | FileCheck --check-prefix=TAR %s
+# RUN: tar tf repro2.tar | FileCheck --check-prefix=TAR2 %s
+
+# TAR: repro/response.txt
+# TAR: repro/version.txt
+# TAR: repro/{{.*}}/foo.o
+
+# TAR2: repro2/response.txt
+# TAR2: repro2/version.txt
+# TAR2: repro2/{{.*}}/foo.o
+
+# RUN: tar xf repro.tar
+# RUN: FileCheck --check-prefix=RSP %s < repro/response.txt
+
+# RSP: -o {{.*}}out.wasm
+# RSP: {{.*}}/foo.o
+
+# RUN: FileCheck %s --check-prefix=VERSION < repro/version.txt
+# VERSION: LLD
+
+.globl  _start
+_start:
+  .functype _start () -> ()
+  end_function

lld/wasm/Driver.cpp

if (config->bsymbolic && !config->shared) {
     warn("-Bsymbolic is only meaningful when combined with -shared");
   }
 
   if (config->globalBase && config->isPic) {
     error("--global-base may not be used with -shared/-pie");
   }
 }
 
+static const char *getReproduceOption(opt::InputArgList &args) {
+  if (auto *arg = args.getLastArg(OPT_reproduce))
+    return arg->getValue();
+  return getenv("LLD_REPRODUCE");
+}
+
 // Force Sym to be entered in the output. Used for -u or equivalent.
 static Symbol *handleUndefined(StringRef name) {
   Symbol *sym = symtab->find(name);
   if (!sym)
     return nullptr;
 
   // Since symbol S may not be used inside the program, LTO may
   // eliminate it. Mark the symbol as "used" to prevent it.
void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
 
   // Handle --version
   if (args.hasArg(OPT_version) || args.hasArg(OPT_v)) {
     lld::outs() << getLLDVersion() << "\n";
     return;
   }
 
   // Handle --reproduce
-  if (auto *arg = args.getLastArg(OPT_reproduce)) {
-    StringRef path = arg->getValue();
+  if (const char *path = getReproduceOption(args)) {
     Expected<std::unique_ptr<TarWriter>> errOrWriter =
         TarWriter::create(path, path::stem(path));
     if (errOrWriter) {
       tar = std::move(*errOrWriter);
       tar->append("response.txt", createResponseFile(args));
       tar->append("version.txt", getLLDVersion() + "\n");
     } else {
       error("--reproduce: " + toString(errOrWriter.takeError()));