Fix Abseil + RE2 support

Depends on Emscripten update in proxy-wasm#172.

Signed-off-by: Martijn Stevenson <[email protected]>

bazel/defs.bzl

@@ -18,8 +18,12 @@ load("@rules_cc//cc:defs.bzl", "cc_binary")
 def _optimized_wasm_cc_binary_transition_impl(settings, attr):
     # TODO(PiotrSikora): Add -flto to copts/linkopts when fixed in emsdk.
     # See: https://github.com/emscripten-core/emsdk/issues/971
+    #
+    # Define STANDALONE_WASM at compile time as well as link time (below).
+    # This fixes Abseil by not including Emscripten JS stacktraces + symbolization.
+    # TODO(martijneken): Remove after Abseil stops using this define.
     return {
-        "//command_line_option:copt": ["-O3"],
+        "//command_line_option:copt": ["-O3", "-DSTANDALONE_WASM"],
         "//command_line_option:cxxopt": [],
         "//command_line_option:linkopt": [],
         "//command_line_option:collect_code_coverage": False,
@@ -102,6 +106,8 @@ def proxy_wasm_cc_binary(
     )
 
     wasm_cc_binary(
+        standalone = True,
+        threads = "off",
         name = "wasm_" + name,
         cc_target = ":proxy_wasm_" + name.rstrip(".wasm"),
         tags = tags + [