Travis CI: Reactivate JDK10 as target

For JDK10, the test suite did not run as the JDK8 binary installed in /usr/bin/ was used for the PRISM runs instead of the JDK10 binaries, even though the JDK10 bin directory comes first on the PATH. This is due to the python startup helpers (when running prism-auto for the tests) fiddling with the PATH variable, prepending /usr/bin/...

So, we now just set the PRISM_JAVA environment variable to the java binary on the PATH from the travis build script, which is then picked up correctly in the prism startup script.

.travis.yml

@@ -10,10 +10,17 @@ language: java
 jdk:
   - oraclejdk8
   - oraclejdk9
-#  - oraclejdk10
+  - oraclejdk10
   
 # compile and run the test suite
-script: cd prism && make && echo 'Compilation successful, running test suite....' && echo && make tests && echo && echo 'Yay'
+# we manually set PRISM_JAVA to the java on the PATH as the python invocation of prism-auto fiddles with the PATH variable...  
+script: >
+  cd prism &&
+  make &&
+  echo 'Compilation successful, running test suite....' && echo &&
+  export PRISM_JAVA=`which java` &&
+  make tests &&
+  echo && echo 'Yay'
 
 
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