androidScreenshotTest: Use full path to emulator

In some systems (like mine) emulator will fail if not called by full path

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

scripts/androidScreenshotTest

@@ -59,7 +59,7 @@ while read line ; do
 done < <(adb devices | cut -f1)
 
 if [ "$emulatorIsRunning" == false ] ; then
-    emulator -writable-system -avd uiComparison -no-snapshot -gpu swiftshader_indirect -no-audio -skin 500x833 &
+    "$(command -v emulator)" -writable-system -avd uiComparison -no-snapshot -gpu swiftshader_indirect -no-audio -skin 500x833 &
 fi
 
 if [ -e $5 ] ; then