[gn build] Force clang_enable_per_target_runtime_dir for Android builds

[aeubanks]

Summary

Since it doesn't work yet.

[aeubanks]

add discourse link

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

 stage2_unix_toolchain("stage2_unix") {
   toolchain_args = {
     current_os = host_os
     current_cpu = host_cpu
   }
 }
 
 if (android_ndk_path != "") {
+  # Android compiler-rt libraries don't really work with per-target runtime
+  # directories yet so force it off.
+  # https://discourse.llvm.org/t/handling-version-numbers-in-per-target-runtime-directories/62717.
   stage2_unix_toolchain("stage2_android_aarch64") {
     toolchain_args = {
       current_os = "android"
       current_cpu = "arm64"
+      clang_enable_per_target_runtime_dir = false
     }
   }
 
   stage2_unix_toolchain("stage2_android_arm") {
     toolchain_args = {
       current_os = "android"
       current_cpu = "arm"
+      clang_enable_per_target_runtime_dir = false
     }
   }
 
   stage2_unix_toolchain("stage2_android_x64") {
     toolchain_args = {
       current_os = "android"
       current_cpu = "x64"
+      clang_enable_per_target_runtime_dir = false
     }
   }
 
   stage2_unix_toolchain("stage2_android_x86") {
     toolchain_args = {
       current_os = "android"
       current_cpu = "x86"
+      clang_enable_per_target_runtime_dir = false
     }
   }
 }
 
 if (host_os == "mac") {
   stage2_unix_toolchain("stage2_ios_aarch64") {
     toolchain_args = {
       current_os = "ios"