Revert "use $(value ...) to reduce escalating double-quoting of dollars"

This reverts commit d2c16eb81a813f709552bd840897047fe98eb131, which caused
JunitTests to call java with a command line containing

  -Dorg.openoffice.test.arg.env=LD_LIBRARY_PATH""

instead of

  -Dorg.openoffice.test.arg.env=LD_LIBRARY_PATH"${LD_LIBRARY_PATH+=$LD_LIBRARY_PATH}"

(and thus caused a build against a local trunk GCC, that requires
LD_LIBRARY_PATH to find the corresponding libstdc++.so.6, to fail).

Change-Id: Ia9613f5a7c6dff1ff6883fc4c079ffaacd1c1b59