Allow building a redistributable package for macOS

This includes building universal binaries (for arm64 and x86_64)
and targeting an older minimum deployment target.

(Before 1919720fdd348ca568b235bf3f1357c198eccd15 in llvm-project,
Jan 2022, building lldb's debugserver failed, if building for macOS
for multiple architectures, or for an architecture other than the
current host.)

build-lldb-mi.sh

@@ -103,6 +103,11 @@ if [ -n "$HOST" ]; then
     CMAKEFLAGS="$CMAKEFLAGS -DCMAKE_FIND_ROOT_PATH_MODE_LIBRARY=ONLY"
 fi
 
+if [ -n "$MACOS_REDIST" ]; then
+    CMAKEFLAGS="$CMAKEFLAGS -DCMAKE_OSX_ARCHITECTURES=arm64;x86_64"
+    CMAKEFLAGS="$CMAKEFLAGS -DCMAKE_OSX_DEPLOYMENT_TARGET=10.9"
+fi
+
 cd lldb-mi
 
 [ -z "$CLEAN" ] || rm -rf $BUILDDIR