Convert bssl-compat build from cmake to bazel

Signed-off-by: Ted Poole <tpoole@redhat.com>

Author: tedjpoole

WORKSPACE

@@ -5,6 +5,12 @@ local_repository(
     path = "bssl-compat",
 )
 
+new_local_repository(
+    name = "llvm",
+    path = "/opt/llvm",
+    build_file = "//bazel/external:llvm.BUILD",
+)
+
 load("//bazel:api_binding.bzl", "envoy_api_binding")
 
 envoy_api_binding()

bazel/BUILD

@@ -572,12 +572,12 @@ config_setting(
 # Alias pointing to the selected version of BoringSSL:
 alias(
     name = "boringssl",
-    actual = "@envoy//bssl-compat:ssl"
+    actual = "@bssl-compat//:ssl"
 )
-
+    
 alias(
     name = "boringcrypto",
-    actual = "@envoy//bssl-compat:crypto"
+    actual = "@bssl-compat//:crypto"
 )
 
 config_setting(

bazel/external/llvm.BUILD

@@ -0,0 +1,26 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+
+licenses(["notice"])  # Apache 2
+
+# libclang-cpp from the local installation of llvm
+# used by the prefixer in bssl-compt
+
+cc_library(
+    name = "libclang-cpp",
+    hdrs = glob([
+        "include/**/*.h",
+        "include/**/*.inc",
+        "include/**/*.def"
+    ]),
+    includes = ["include"],
+    defines = [
+        "LLVM_LIBRARY_DIR=\\\"/opt/llvm/lib/\\\"",
+    ],
+    linkopts = [
+        "-L/opt/llvm/lib",
+        "-lclang-cpp",
+        "-lstdc++",
+        "-Wl,-rpath,/opt/llvm/lib",
+    ],
+    visibility = ["//visibility:public"],
+)

bazel/repositories.bzl

@@ -140,11 +140,11 @@ def envoy_dependencies(skip_targets = []):
     # Binding to an alias pointing to the bssl-compat layer
     native.bind(
         name = "ssl",
-        actual = "@envoy//bssl-compat:ssl",
+        actual = "@bssl-compat//:ssl",
     )
     native.bind(
         name = "crypto",
-        actual = "@envoy//bssl-compat:crypto",
+        actual = "@bssl-compat//:crypto",
     )
 
     # The long repo names (`com_github_fmtlib_fmt` instead of `fmtlib`) are