Fix helloworld zlib include directory confusion in run_distrib_test_cmake.bat

We have to give cmake the explicit zlib location as the internal testing
environment has C:/msys64/usr/bin in the PATH and zlib-devel installed.
cmake has heuristics in find_package which sees this /bin suffix in PATH
and adds C:/msys64/usr/ to the find_package search locations. Doing a
find_package(zlib) in this environment makes the find module for it (FindZLIB)
find the header zlib.h in C:/msys64/usr/include while the library will still
be taken from the testinstall location masking the issue in the log. To satisfy
the dependency cmake adds C:/msys64/usr/include as an include directory. This
makes cl.exe build with mixed C and C++ standard lib headers breaking the
build.

This issue was previously masked by cmake writing absolute paths for zlib and
other dependencies into the grpc cmake exports.

test/distrib/cpp/run_distrib_test_cmake.bat

@@ -64,7 +64,7 @@ mkdir cmake
 cd cmake
 mkdir build
 cd build
-cmake -DCMAKE_INSTALL_PREFIX=%INSTALL_DIR% -DOPENSSL_ROOT_DIR=%OPENSSL_DIR% -DOPENSSL_INCLUDE_DIR=%OPENSSL_DIR%/include ../.. || goto :error
+cmake -DCMAKE_INSTALL_PREFIX=%INSTALL_DIR% -DOPENSSL_ROOT_DIR=%OPENSSL_DIR% -DOPENSSL_INCLUDE_DIR=%OPENSSL_DIR%/include -DZLIB_LIBRARY=%INSTALL_DIR%/lib/zlibstatic.lib -DZLIB_INCLUDE_DIR=%INSTALL_DIR%/include ../.. || goto :error
 cmake --build . --config Release || goto :error
 cd ../../../../..