Rollup merge of rust-lang#39950 - ishitatsuyuki:stop-trashing-ldpath,…

… r=alexcrichton

bootstrap: stop trashing (DY)LD_LIBRARY_PATH

This generated an ugly error with fakeroot before.

src/bootstrap/bootstrap.py

@@ -355,8 +355,12 @@ def build_bootstrap(self):
  env = os.environ.copy()
  env["CARGO_TARGET_DIR"] = build_dir
  env["RUSTC"] = self.rustc()
- env["LD_LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib")
- env["DYLD_LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib")
+ env["LD_LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib") + \
+ (os.pathsep + env["LD_LIBRARY_PATH"]) \
+ if "LD_LIBRARY_PATH" in env else ""
+ env["DYLD_LIBRARY_PATH"] = os.path.join(self.bin_root(), "lib") + \
+ (os.pathsep + env["DYLD_LIBRARY_PATH"]) \
+ if "DYLD_LIBRARY_PATH" in env else ""
  env["PATH"] = os.path.join(self.bin_root(), "bin") + \
  os.pathsep + env["PATH"]
  if not os.path.isfile(self.cargo()):