Build.sh: work around Git for Windows' lack of stat(1)

The Git for Windows installer does not install the stat(1) utility. But
it has GNU date(1). And that version of date(1) has the -r option
which we can use instead of stat(1) to get at the mtime of a file.

Noticed by Olexandra Ovsiy in bug 628.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Build.sh

@@ -176,28 +176,31 @@ fi
 PATH="$PATH:$(get_java_home)/bin:$(get_java_home)/../bin"
 export PATH
 
+# Thanks, MacOSX (or for that matter, BSD), and Windows, for easy, standard
+# ways to get the mtime of a file.
+
+get_mtime () {
+	stat -c %Y "$1"
+}
+
 # JAVA_HOME needs to be a DOS path for Windows from here on
 case "$UNAME_S" in
 MINGW*)
 	export JAVA_HOME="$(cd "$JAVA_HOME" && pwd -W)"
+	get_mtime () {
+		date -r "$1" +%s
+	}
 	;;
 CYGWIN*)
 	export JAVA_HOME="$(cygpath -d "$JAVA_HOME")"
 	;;
+Darwin*)
+	get_mtime () {
+		stat -f %m "$1"
+	}
+	;;
 esac
 
-# Thanks, MacOSX (or for that matter, BSD)
-
-get_mtime () {
-        stat -c %Y "$1"
-}
-if test Darwin = "$(uname -s 2> /dev/null)"
-then
-        get_mtime () {
-                stat -f %m "$1"
-        }
-fi
-
 # Figure out whether $2 (the destination) is newer than $1 (the source).
 # If $2 is a SNAPSHOT .jar, must not be older than a day, either.
 #