Update cmake-errors.yml again and again and again and again and again and

Author: mulle-nat

.github/workflows/cmake-errors.yml

@@ -78,7 +78,7 @@ jobs:
           if [ "$RUNNER_OS" == "Windows" ]
           then
             INSTALL_DIR="$GITHUB_WORKSPACE\\usr"
-            CMAKE_INSTALL_DIR="$(cygpath -u "$INSTALL_DIR")"
+            CMAKE_INSTALL_DIR="$(sed 's/\\/\//g' <<< "$INSTALL_DIR")"  # sic, cygpath no good for cmake
             SRC_DIR="$GITHUB_WORKSPACE\\tmp"
             MULLE_CORE_SRC_DIR="$SRC_DIR\\mulle-core"
             MULLE_ATINIT_SRC_DIR="$SRC_DIR\\mulle-atinit"