replace single with double quotes to enable variable substitution

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1884388 13f79535-47bb-0310-9956-ffa450edef68

build.gradle

 
         compile project(':main')
         compile project(':scratchpad')		// TODO: get rid of this dependency!
-        compile files('../../build/dist/maven/poi-ooxml-full/poi-ooxml-full-${version}.jar')
+        compile files("../../build/dist/maven/poi-ooxml-full/poi-ooxml-full-${version}.jar")
 
         testCompile "junit:junit:${junitVersion}"
         testCompile "org.mockito:mockito-core:${mockitoVersion}"
 
         compile "org.apache.xmlbeans:xmlbeans:${xmlbeansVersion}"
 
-        compile files('../../build/dist/maven/poi-ooxml-full/poi-ooxml-full-${version}.jar')
+        compile files("../../build/dist/maven/poi-ooxml-full/poi-ooxml-full-${version}.jar")
         compile "org.apache.commons:commons-compress:${commonsCompressVersion}"
     }
 
 
         testCompile "org.apache.xmlbeans:xmlbeans:${xmlbeansVersion}"
 
-        testCompile files('../../build/dist/maven/poi-ooxml-full/poi-ooxml-full-${version}.jar')
+        testCompile files("../../build/dist/maven/poi-ooxml-full/poi-ooxml-full-${version}.jar")
         testCompile files(this.project(':ooxml').sourceSets.test.runtimeClasspath)
     }