Fix JavaRegression test classpath for Windows

ExternalData.cmake was interpreting the classpath value as a semicolon separated
CMake list. To avoid this, enclosed the value in double quotes.

Change-Id: Icb29c596afe39571b982f3e983b619357a33bc89
Merge topic 'fix_JavaRegression_classpath' into master

5632235d Fix JavaRegression test classpath for Windows