Change backslashes to forward slashes in clang path name.

Author: cmtice

.ci/monolithic-windows.sh

@@ -23,8 +23,8 @@ runtimes_targets="${4}"
 start-group "CMake"
 pip install -q -r "${MONOREPO_ROOT}"/.ci/all_requirements.txt
 
-export CC=C:\clang\clang-msvc\bin\clang-cl.exe
-export CXX=C:\clang\clang-msvc\bin\clang-cl.exe
+export CC=C:/clang/clang-msvc/bin/clang-cl.exe
+export CXX=C:/clang/clang-msvc/bin/clang-cl.exe
 export LD=link
 
 # The CMAKE_*_LINKER_FLAGS to disable the manifest come from research