configure: add --ninja option

On Windows it is not possible to invoke a Python script as $NINJA.
If ninja is present use it directly, while if it is not we can
keep using ninjatool.

Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -568,6 +568,7 @@ rng_none="no"
 secret_keyring=""
 libdaxctl=""
 meson=""
+ninja=""
 skip_meson=no
 gettext=""
 
@@ -1052,6 +1053,8 @@ for opt do
   ;;
   --meson=*) meson="$optarg"
   ;;
+  --ninja=*) ninja="$optarg"
+  ;;
   --smbd=*) smbd="$optarg"
   ;;
   --extra-cflags=*)
@@ -1820,6 +1823,7 @@ Advanced options (experts only):
   --python=PYTHON          use specified python [$python]
   --sphinx-build=SPHINX    use specified sphinx-build [$sphinx_build]
   --meson=MESON            use specified meson [$meson]
+  --ninja=NINJA            use specified ninja [$ninja]
   --smbd=SMBD              use specified smbd [$smbd]
   --with-git=GIT           use specified git [$git]
   --static                 enable static build [$static]
@@ -2058,6 +2062,16 @@ case "$meson" in
     *) meson=$(command -v meson) ;;
 esac
 
+# Probe for ninja (used for compdb)
+
+if test -z "$ninja"; then
+    for c in ninja ninja-build samu; do
+        if has $c; then
+            ninja=$(command -v "$c")
+            break
+        fi
+    done
+fi
 
 # Check that the C compiler works. Doing this here before testing
 # the host CPU ensures that we had a valid CC to autodetect the
@@ -8197,7 +8211,7 @@ fi
 mv $cross config-meson.cross
 
 rm -rf meson-private meson-info meson-logs
-NINJA=$PWD/ninjatool $meson setup \
+NINJA=${ninja:-$PWD/ninjatool} $meson setup \
         --prefix "${pre_prefix}$prefix" \
         --libdir "${pre_prefix}$libdir" \
         --libexecdir "${pre_prefix}$libexecdir" \