Revert "TensorFlow June pin update & PyTorch/XLA c++17 migration (follow up) (#3794)"

This reverts commit 6639bcc.

Author: JackCaoG

build_torch_xla_libs.sh

@@ -54,10 +54,9 @@ if [[ ! -z "$BAZEL_JOBS" ]]; then
   MAX_JOBS="--jobs=$BAZEL_JOBS"
 fi
 
-OPTS+=(--cxxopt="-std=c++17")
+OPTS+=(--cxxopt="-std=c++14")
 if [[ $(basename -- $CC) =~ ^clang ]]; then
   OPTS+=(--cxxopt="-Wno-c++11-narrowing")
-  OPTS+=(--cxxopt="-Wno-c++14-narrowing")
 fi
 
 if [[ "$XLA_CUDA" == "1" ]]; then

setup.py

@@ -303,7 +303,7 @@ def make_relative_rpath(path):
 
 
 extra_compile_args = [
-    '-std=c++17',
+    '-std=c++14',
     '-Wno-sign-compare',
     '-Wno-deprecated-declarations',
     '-Wno-return-type',

test/cpp/CMakeLists.txt

@@ -43,8 +43,6 @@ ExternalProject_Add(
   CMAKE_ARGS
     "-DCMAKE_CXX_FLAGS=-D_GLIBCXX_USE_CXX11_ABI=${PT_CXX_ABI}")
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
-
 ExternalProject_Get_Property(googletest SOURCE_DIR)
 
 set(TORCH_XLA_TEST_SOURCES