[roottest] Run h2root in a subprocess.

Running h2root in a subprocess will allow for marking the test as
WILL_FAIL in CTest. If it's not running as a subprocess, the WILL_FAIL
has no effect, since it checks the exit status.

Author: hageboeck

roottest/root/hist/CMakeLists.txt

@@ -8,7 +8,7 @@ ROOTTEST_ADD_TEST(assertSparseToTHn
 
 if(fortran AND CMAKE_Fortran_COMPILER AND NOT CMAKE_Fortran_COMPILER_ID STREQUAL Intel)
   ROOTTEST_ADD_TEST(h2root
-                    COMMAND h2root mb4i1.hbook
+                    COMMAND ${CMAKE_COMMAND} -E env h2root mb4i1.hbook
                     COPY_TO_BUILDDIR mb4i1.hbook
                     OUTREF h2root.ref)
 endif()