Summary: Added a new test_env.txt file to capture common shell variable. Added concept of COMPILEJAVA for use when TESTJAVA is a JRE. If COMPILEJAVA not set then TESTJAVA will be the default with assumption it is a JDK.
Reviewed-by: kvn, brutisso, coleenp

7107135: Stack guard pages are no more protected after loading a shared library with executable stack
Summary: Detect the execstack attribute of the loaded library and attempt to fix the stack guard using Safepoint op.
Reviewed-by: dholmes, zgu
Contributed-by: ioi.lam@oracle.com