Simplify the platform-specific definitions

It seems that `--cxxopt=-D_GLIBCXX_USE_CXX11_ABI=1` works on all
platforms (possibly because the Windows compiler ignores altogether?).
We may as well pull that out into a single build setting that's common
for all platforms.

Author: mhucka

.bazelrc

@@ -24,19 +24,16 @@ common --verbose_failures
 common --enable_platform_specific_config
 
 build:linux --copt=-std=c++17
-build:linux --copt=-D_GLIBCXX_USE_CXX11_ABI=1
 build:linux --cxxopt=-std=c++17
-build:linux --cxxopt=-D_GLIBCXX_USE_CXX11_ABI=1
 
 build:macos --copt=-std=c++17
-build:macos --copt=-D_GLIBCXX_USE_CXX11_ABI=1
 build:macos --cxxopt=-std=c++17
-build:macos --cxxopt=-D_GLIBCXX_USE_CXX11_ABI=1
 
 build:windows --copt=/std:c++17
-build:windows --copt=-D_GLIBCXX_USE_CXX11_ABI=1
 build:windows --cxxopt=/std:c++17
-build:windows --cxxopt=-D_GLIBCXX_USE_CXX11_ABI=1
+
+build --copt=-D_GLIBCXX_USE_CXX11_ABI=1
+build --cxxopt=-D_GLIBCXX_USE_CXX11_ABI=1
 
 # Test flags
 test --test_output=errors