[gn build] Support building x86/64 Android libraries

[aeubanks]

use i686

[aeubanks]

no zdefs

[hans]

lgtm

llvm/utils/gn/build/BUILD.gn

config("no_rtti") {
   }
   cflags_objcc = cflags_cc
 }
 
 config("zdefs") {
   # -Wl,-z,defs doesn't work with sanitizers.
   # https://clang.llvm.org/docs/AddressSanitizer.html
   if (current_os != "ios" && current_os != "mac" && current_os != "win" &&
-      !(use_asan || use_tsan || use_ubsan)) {
+      current_os != "android" && !(use_asan || use_tsan || use_ubsan)) {
     ldflags = [ "-Wl,-z,defs" ]
   }
 }
 
 # To make an archive that can be distributed, you need to remove this config and
 # set complete_static_lib.
 config("thin_archive") {
   if (current_os != "ios" && current_os != "mac" && current_os != "win") {

llvm/utils/gn/build/toolchain/BUILD.gn

if (android_ndk_path != "") {
   }
 
   stage2_unix_toolchain("stage2_android_arm") {
     toolchain_args = {
       current_os = "android"
       current_cpu = "arm"
     }
   }
+
+  stage2_unix_toolchain("stage2_android_x64") {
+    toolchain_args = {
+      current_os = "android"
+      current_cpu = "x64"
+    }
+  }
+
+  stage2_unix_toolchain("stage2_android_x86") {
+    toolchain_args = {
+      current_os = "android"
+      current_cpu = "x86"
+    }
+  }
 }
 
 if (host_os == "mac") {
   stage2_unix_toolchain("stage2_ios_aarch64") {
     toolchain_args = {
       current_os = "ios"
       current_cpu = "arm64"
     }

llvm/utils/gn/build/toolchain/target_flags.gni

 target_ldflags = []
 
 if (current_os == "android") {
   target_flags += [
     "--target=$llvm_current_triple",
     "--sysroot=$android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64/sysroot",
     "--gcc-toolchain=$android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64",
   ]
-  target_ldflags += [ "-static-libstdc++" ]
+  target_ldflags += [
+    "-static-libstdc++",
+    "--unwindlib=none",
+  ]
   if (current_cpu == "arm") {
     target_flags += [ "-march=armv7-a" ]
   }
 } else if (current_os == "ios") {
   if (current_cpu == "arm64") {
     target_flags += [
       "-arch",
       "arm64",
target_ldflags += [
       "x86_64",
     ]
   }
 } else if (current_os == "baremetal") {
   target_flags += [ "--target=$llvm_current_triple" ]
 }
 
 if (current_cpu == "x86") {
-  target_flags = [ "-m32" ]
+  target_flags += [ "-m32" ]
 }

llvm/utils/gn/secondary/compiler-rt/target.gni

 import("//clang/resource_dir.gni")
 import("//clang/runtimes.gni")
 
 if (current_cpu == "x86") {
+  if (current_os == "android") {
+    crt_current_target_arch = "i686"
+  } else {
     crt_current_target_arch = "i386"
+  }
 } else if (current_cpu == "x64") {
   crt_current_target_arch = "x86_64"
 } else if (current_cpu == "arm") {
   crt_current_target_arch = "arm"
 } else if (current_cpu == "arm64") {
   crt_current_target_arch = "aarch64"
 } else if (current_cpu == "ppc64") {
   crt_current_target_arch = "powerpc64le"

llvm/utils/gn/secondary/libunwind/src/BUILD.gn

if (current_os == "mac") {
   unwind_sources += [ "Unwind_AppleExtras.cpp" ]
 }
 
 if (current_os == "android") {
   if (current_cpu == "arm64") {
     unwind_output_dir = "$crt_current_out_dir/aarch64"
   } else if (current_cpu == "arm") {
     unwind_output_dir = "$crt_current_out_dir/arm"
+  } else if (current_cpu == "x64") {
+    unwind_output_dir = "$crt_current_out_dir/x86_64"
+  } else if (current_cpu == "x86") {
+    unwind_output_dir = "$crt_current_out_dir/i686"
   }
 } else {
   unwind_output_dir = runtimes_dir
 }
 
 config("unwind_config") {
   cflags = []
   cflags_c = [ "-std=c99" ]

llvm/utils/gn/secondary/llvm/lib/Target/targets.gni

if (android_ndk_path != "") {
   if (llvm_build_AArch64) {
     supported_android_toolchains +=
         [ "//llvm/utils/gn/build/toolchain:stage2_android_aarch64" ]
   }
   if (llvm_build_ARM) {
     supported_android_toolchains +=
         [ "//llvm/utils/gn/build/toolchain:stage2_android_arm" ]
   }
+  if (llvm_build_X86) {
+    supported_android_toolchains += [
+      "//llvm/utils/gn/build/toolchain:stage2_android_x64",
+      "//llvm/utils/gn/build/toolchain:stage2_android_x86",
+    ]
+  }
 }

llvm/utils/gn/secondary/llvm/triples.gni

 if (current_cpu == "x86") {
   if (current_os == "linux") {
     llvm_current_triple = "i386-unknown-linux-gnu"
   } else if (current_os == "win") {
     llvm_current_triple = "i386-pc-windows-msvc"
+  } else if (current_os == "android") {
+    llvm_current_triple = "i686-linux-android29"
   }
 } else if (current_cpu == "x64") {
   if (current_os == "freebsd") {
     llvm_current_triple = "x86_64-unknown-freebsd"
   } else if (current_os == "linux") {
     llvm_current_triple = "x86_64-unknown-linux-gnu"
   } else if (current_os == "ios" || current_os == "mac") {
     llvm_current_triple = "x86_64-apple-darwin"
   } else if (current_os == "win") {
     llvm_current_triple = "x86_64-pc-windows-msvc"
+  } else if (current_os == "android") {
+    llvm_current_triple = "x86_64-linux-android29"
   }
 } else if (current_cpu == "arm") {
   if (current_os == "android") {
     llvm_current_triple = "arm-linux-androideabi29"
   }
 } else if (current_cpu == "arm64") {
   if (current_os == "android") {
     llvm_current_triple = "aarch64-linux-android29"