In XCode clang 11 I get: No template named 'initializer_list' in namespace 'std'

When someone on my team executes:

/Applications/CLion.app/Contents/bin/cmake/mac/bin/cmake .. -G Xcode

using XCode 10, and then opens the xcodeproj folder, Xcode starts and everything compiles.

In his project.pbxproj file are:

OTHER_CPLUSPLUSFLAGS = "-std=c++11 -pthread -fstrict-aliasing -Wall -Wcast-qual -Wextra -Wformat -Wpedantic -Wswitch-default -Wno-unknown-pragmas
OTHER_LDFLAGS = " -Wl,-search_paths_first -Wl,-headerpad_max_install_names  $HEAD/sdsp/metrics/test/build/sws-metrics/Release/libsws-metrics.a";

It does not do the same thing when I do this using:

Apple clang version 11.0.0 (clang-1100.0.33.17)

I get errors:

• No template named 'initializer_list' in namespace 'std'
• A space is required between consecutive right angle brackets (use '> >')

And my OTHER_ variables are blank. I tried setting these to be like his- it didn't help.

In the project I tried all the various options for

Apple Clang - Language
  C Language Dialect - Compiler Default, c11, gnu11
Apple Clang - Language - C++
  C++ Language Dialect - C++11 [-std=c++11] (and gnu11 and the 14 and 17's)
  C++ Standard Library - Compiler Default, libstdc++, libc++
Apple Clang - Warnings - C++
  Using C++11 extensions in earlier versions of C++ - was No and I tried that and Yes

Nothing works.

We both create the makefiles from the same folder with:

/Applications/CLion.app/Contents/bin/cmake/mac/bin/cmake .. -G Xcode

I also tried the 3.17.0 cmake I had in homebrew, and after upgrading it to 3.18.1. No difference.

Any idea what to do?

(I have an old XCode10.3, but it won't run- it tries to "install additional components" and fails...)