Fix a compilation error for com_lightstep_tracer_cpp

bazel/com_lightstep_tracer_cpp.patch

@@ -0,0 +1,12 @@
+diff --git a/bazel/lightstep_build_system.bzl b/bazel/lightstep_build_system.bzl
+index cd896c8..bdbba6d 100644
+--- a/bazel/lightstep_build_system.bzl
++++ b/bazel/lightstep_build_system.bzl
+@@ -46,6 +46,7 @@ def lightstep_copts(is_3rd_party=False):
+       "-Wno-overloaded-virtual",
+       "-Wvla",
+       "-std=c++11",
++      "-fsigned-char",
+   ]
+
+ def lightstep_linkopts():

bazel/repositories.bzl

@@ -411,7 +411,14 @@ def _io_opentracing_cpp():
     )
 
 def _com_lightstep_tracer_cpp():
-    _repository_impl("com_lightstep_tracer_cpp")
+    _repository_impl(
+        name = "com_lightstep_tracer_cpp",
+        patch_args = ["-p1"],
+        # Workaround for GCC architecture specific optimization about 'char' type
+        # on different arches: arm64, ia64, ppc64, ...
+        # Ref: https://wiki.debian.org/ArchitectureSpecificsMemo
+        patches = ["@envoy//bazel:com_lightstep_tracer_cpp.patch"],
+    )
     native.bind(
         name = "lightstep",
         actual = "@com_lightstep_tracer_cpp//:manual_tracer_lib",