Test Antlr CMake fix

runtime-builder

Pulls in Antlr4 using FetchContent and simply builds the runtime. On Windows, build with:

build-runtime.bat
build-runtime-with-fix.bat

On Linux, build with:

build-runtime.sh
build-runtime-with-fix.sh

This will build two versions of the runtime,
one with the latest commit from the official Antlr4 git repo and
one from my fork with the cmake fix.

Built artifacts are placed into a folder called install in the root of the repo.

test-project

Build scripts for runtime-builder must be run before running these build scripts.

This is a simple test project with a single main.cpp file that has #include antlr4-runtime.h.
The with-fix version will find antlr4-runtime from the install-with-fix folder and the non-with-fix
version will find antlr4-runtime from the install folder.

On Windows, build with:

build-test.bat
build-test-with-fix.bat

On Linux, build with:

build-test.sh
build-test-with-fix.sh

build-test should fail to build because it fails to find antlr4-runtime.h

build-test-with-fix should correctly build because the include directories are properly set in antrl4_static and antlr4_shared targets.

There is also output on configure that shows the includes directories set on the antlr4_static and antlr4_shared targets. Look for antlr4_static_RUNTIME_INTERFACE_INCLUDES in the configure output.