Check for macOS Catalina and use appropriate tools

Since RenderScript can no longer be compiled on macOS Catalina
because Catalina cannot run 32bit binaries and Google failed
to provide a 64bit compiler in time. Now, as if that wasn't
bad enough, the new build tools that provide a 64bit compiler
don't work on any other system than macOS unfortunately.

For details on the issue see:
https://issuetracker.google.com/issues/142590626

build.gradle

@@ -1,9 +1,26 @@
 buildscript {
-	ext.kotlin_version = '1.3.61'
-	ext.tools_version = '3.5.3'
-	ext.build_tools_version = '28.0.3'
-	ext.sdk_version = 29
-	ext.support_version = '25.3.1'
+	// Since RenderScript can no longer be compiled on macOS Catalina
+	// because Catalina cannot run 32bit binaries and Google failed
+	// to provide a 64bit compiler in time. Now, as if that wasn't
+	// bad enough, the new build tools that provide a 64bit compiler
+	// don't work on any other system than macOS unfortunately.
+	def isCatalina = {
+		if (System.properties['os.name'] == 'Mac OS X') {
+			def numbers = System.properties['os.version'].split('\\.')
+			if (numbers.length > 1) {
+				return numbers[1].toInteger() >= 15
+			}
+		}
+		return false
+	}()
+
+	ext {
+		kotlin_version = '1.3.61'
+		tools_version = isCatalina ? '3.6.0-rc02' : '3.5.3'
+		build_tools_version = isCatalina ? '29.0.3' : '28.0.3'
+		sdk_version = 29
+		support_version = '25.3.1'
+	}
 
 	repositories {
 		google()

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip