xCode CommandLine Tools SDK Error - files exist, pls help

Running Mojave 10.14.6 with xCode Version 11.3.1 (11C504)

I'm trying to build from source via terminal a software package and am getting the following error:

# Framework

cd breakpad/src/client/mac/ && xcodebuild MACOSX_DEPLOYMENT_TARGET=10.11 -sdk /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk WARNING_CFLAGS=-Werror=partial-availability OTHER_CFLAGS=-fno-stack-check -arch x86_64 CLANG_CXX_LIBRARY=libc++

xcodebuild: error: SDK "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk" cannot be located.

make: *** [.breakpad] Error 64

The files however ARE there:

pwd

/Library/Developer/CommandLineTools/SDKs

McKinley:SDKs XY15$ ls -la

total 0

drwxr-xr-x 4 XY15 staff 128 Jul 23 2019 .

drwxr-xr-x 6 XY15 staff 192 Jan 31 2019 ..

drwxr-xr-x 7 XY15 staff 224 Jul 23 2019 MacOSX.sdk

lrwxr-xr-x 1 XY15 staff 10 Jul 23 2019 MacOSX10.14.sdk -> MacOSX.sdk

McKinley:SDKs XY15$

The source code developer's recommendation is that "only apple knows why this happens, remove commandline tools or delete the directory for them". That doesn't seem acceptable.

What could be causing this and HOW can I fix it? TIA.