Revert "[infra] Roll clang to match the version used by Flutter"

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   # The optimization level to use for debug builds.
   if (is_android) {
     # On Android we kind of optimize some things that don't affect debugging
     # much even when optimization is disabled to get the binary size down.
     debug_optimization_level = "s"
@@ skipping 112 matching lines @@
     # well-defined C/C++ and Clang can optimize such checks away in
     # release builds, but they may be used in asserts in debug builds.
     extra_flags = [
       "-Wno-undefined-bool-conversion",
       "-Wno-tautological-undefined-compare",
     ]
     cflags_cc += extra_flags
     cflags_objcc += extra_flags
   }
 
+  if (is_clang) {
+    # This is here so that all files get recompiled after a clang roll and
+    # when turning clang on or off. (defines are passed via the command line,
+    # and build system rebuild things when their commandline changes). Nothing
+    # should ever read this define.
+    defines +=
+        [ "CR_CLANG_REVISION=" + exec_script("//tools/clang/scripts/update.py",
+                                             [ "--print-revision" ],
+                                             "trim string") ]
+  }
+
   # Mac-specific compiler flags setup.
   # ----------------------------------
   if (is_mac) {
     # These flags are shared between the C compiler and linker.
     common_mac_flags = [ "-fno-exceptions" ]
 
     # CPU architecture.
     if (current_cpu == "x64") {
       common_mac_flags += [
         "-arch",
@@ skipping 204 matching lines @@
       cflags += [ "-mllvm -asan-globals=0" ]
     }
 
     defines += [ "ANDROID" ]
 
     # The NDK has these things, but doesn't define the constants
     # to say that it does. Define them here instead.
     defines += [ "HAVE_SYS_UIO_H" ]
 
     # Use gold for Android for most CPU architectures.
-    if (current_cpu == "x86" || current_cpu == "x64" || current_cpu == "arm" ||
-        current_cpu == "arm64") {
+    if (current_cpu == "x86" || current_cpu == "x64" || current_cpu == "arm") {
       ldflags += [ "-fuse-ld=gold" ]
       if (is_clang) {
         # Let clang find the ld.gold in the NDK.
         ldflags += [ "--gcc-toolchain=" +
                      rebase_path(android_toolchain_root, root_build_dir) ]
       }
     }
 
     ldflags += [
-      # Don't re-export visible symbols from libraries.
-      "-Wl,--exclude-libs,ALL",
+      # Don't allow visible symbols from libgcc or libc++ to be
+      # re-exported.
+      "-Wl,--exclude-libs=libgcc.a",
+      "-Wl,--exclude-libs=libc++_static.a",
     ]
     if (current_cpu == "arm") {
       ldflags += [
         # Enable identical code folding to reduce size.
         "-Wl,--icf=safe",
       ]
     }
 
     if (is_clang) {
       if (current_cpu == "arm") {
         cflags += [ "--target=arm-linux-androideabi" ]
         ldflags += [ "--target=arm-linux-androideabi" ]
-      } else if (current_cpu == "arm64") {
-        cflags += [ "--target=aarch64-linux-android" ]
-        ldflags += [ "--target=aarch64-linux-android" ]
       } else if (current_cpu == "x86") {
-        cflags += [ "--target=i686-linux-androideabi" ]
-        ldflags += [ "--target=i686-linux-androideabi" ]
-      } else if (current_cpu == "x64") {
-        cflags += [ "--target=x86_64-linux-androideabi" ]
-        ldflags += [ "--target=x86_64-linux-androideabi" ]
+        cflags += [ "--target=x86-linux-androideabi" ]
+        ldflags += [ "--target=x86-linux-androideabi" ]
       }
     }
   }
 
   # Assign any flags set for the C compiler to asmflags so that they are sent
   # to the assembler. The Windows assembler takes different types of flags
   # so only do so for posix platforms.
   if (is_posix) {
     asmflags += cflags
     asmflags += cflags_c
@@ skipping 69 matching lines @@
           rebase_path("$android_libcpp_root/libcxx/include", root_build_dir),
       "-isystem" + rebase_path(
               "$android_ndk_root/sources/cxx-stl/llvm-libc++abi/libcxxabi/include",
               root_build_dir),
       "-isystem" +
           rebase_path("$android_ndk_root/sources/android/support/include",
                       root_build_dir),
     ]
 
     lib_dirs += [ "$android_libcpp_root/libs/$android_app_abi" ]
+    libs += [ "$android_libcpp_library" ]
 
-    libs += [
-      "$android_libcpp_library",
-      "c++abi",
-      "android_support",
-    ]
-
-    if (current_cpu == "arm") {
-      libs += [ "unwind" ]
+    if (current_cpu == "mipsel") {
+      libs += [
+        # ld linker is used for mips Android, and ld does not accept library
+        # absolute path prefixed by "-l"; Since libgcc does not exist in mips
+        # sysroot the proper library will be linked.
+        # TODO(gordanac): Remove once gold linker is used for mips Android.
+        "gcc",
+      ]
+    } else {
+      libs += [
+        # Manually link the libgcc.a that the cross compiler uses. This is
+        # absolute because the linker will look inside the sysroot if it's not.
+        rebase_path(android_libgcc_file),
+      ]
     }
 
     libs += [
-      "gcc",
       "c",
       "dl",
       "m",
     ]
 
     # Clang with libc++ does not require an explicit atomic library reference.
     if (!is_clang) {
       libs += [ "atomic" ]
     }
   }
@@ skipping 271 matching lines @@
       cflags = [ "/Zi" ]  # Produce PDB file, no edit and continue.
     }
     ldflags = [ "/DEBUG" ]
   } else {
     cflags = [
       "-g3",
       "-ggdb3",
     ]
   }
 }