diff --git a/build-compiler-rt.sh b/build-compiler-rt.sh
index c83dd41..eb261ad 100755
--- a/build-compiler-rt.sh
+++ b/build-compiler-rt.sh
@@ -70,9 +70,19 @@ for arch in $ARCHS; do
         libarchname=i386
         ;;
     esac
+
+    case $(uname) in
+    MINGW*)
+        CMAKE_GENERATOR="MSYS Makefiles"
+        ;;
+    *)
+        ;;
+    esac
+
     mkdir -p build-$arch$BUILD_SUFFIX
     cd build-$arch$BUILD_SUFFIX
     cmake \
+        ${CMAKE_GENERATOR+-G} "$CMAKE_GENERATOR" \
         -DCMAKE_BUILD_TYPE=Release \
         -DCMAKE_C_COMPILER=$arch-w64-mingw32-clang \
         -DCMAKE_CXX_COMPILER=$arch-w64-mingw32-clang++ \
diff --git a/build-libcxx.sh b/build-libcxx.sh
index e4245a9..a6bafd6 100755
--- a/build-libcxx.sh
+++ b/build-libcxx.sh
@@ -68,6 +68,14 @@ fi
 LIBCXX=$(pwd)/libcxx
 MERGE_ARCHIVES=$(pwd)/merge-archives.sh
 
+case $(uname) in
+MINGW*)
+    CMAKE_GENERATOR="MSYS Makefiles"
+    ;;
+*)
+    ;;
+esac
+
 build_all() {
     type="$1"
     if [ "$type" = "shared" ]; then
@@ -86,6 +94,7 @@ build_all() {
         # to the compiler flags; manually add it here to avoid noisy warnings
         # that normally are suppressed.
         cmake \
+            ${CMAKE_GENERATOR+-G} "$CMAKE_GENERATOR" \
             -DCMAKE_BUILD_TYPE=Release \
             -DCMAKE_INSTALL_PREFIX=$PREFIX/$arch-w64-mingw32 \
             -DCMAKE_C_COMPILER=$arch-w64-mingw32-clang \
@@ -137,6 +146,7 @@ build_all() {
             LIBCXXABI_VISIBILITY_FLAGS="-D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS"
         fi
         cmake \
+            ${CMAKE_GENERATOR+-G} "$CMAKE_GENERATOR" \
             -DCMAKE_BUILD_TYPE=Release \
             -DCMAKE_INSTALL_PREFIX=$PREFIX/$arch-w64-mingw32 \
             -DCMAKE_C_COMPILER=$arch-w64-mingw32-clang \
@@ -174,6 +184,7 @@ build_all() {
             LIBCXX_VISIBILITY_FLAGS="-D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS"
         fi
         cmake \
+            ${CMAKE_GENERATOR+-G} "$CMAKE_GENERATOR" \
             -DCMAKE_BUILD_TYPE=Release \
             -DCMAKE_INSTALL_PREFIX=$PREFIX/$arch-w64-mingw32 \
             -DCMAKE_C_COMPILER=$arch-w64-mingw32-clang \
diff --git a/build-llvm.sh b/build-llvm.sh
index 0143bcc..1a7c0ab 100755
--- a/build-llvm.sh
+++ b/build-llvm.sh
@@ -69,6 +69,14 @@ fi
 if [ -n "$(which ninja)" ]; then
     CMAKE_GENERATOR="Ninja"
     NINJA=1
+else
+    case $(uname) in
+    MINGW*)
+        CMAKE_GENERATOR="MSYS Makefiles"
+        ;;
+    *)
+        ;;
+    esac
 fi
 
 if [ -n "$HOST" ]; then