CTest: add an ENVIRONMENT_MODIFICATION property

This property allows projects to modify environment variables at test
time rather than trying to guess what the state should be based on what
is present at configure time. Of particular interest is the ability to
use a `PATH` present at test time while adding entries known to be
necessary for the test itself.

There are multiple operations provided to modify variables, including:

  - setting and unsetting
  - appending and prepending as:
    - strings
    - path lists
    - CMake lists

Additionally, a `reset` action is provided to cancel any prior
modifications to that particular variable in the case of incremental
additions to the test property.

1 files changed, 1 insertions, 0 deletions

diff --git a/Source/CTest/cmCTestRunTest.h b/Source/CTest/cmCTestRunTest.h
index a4981c3..2082156 100644
--- a/Source/CTest/cmCTestRunTest.h
+++ b/Source/CTest/cmCTestRunTest.h
@@ -113,6 +113,7 @@ private:
   void ExeNotFound(std::string exe);
   bool ForkProcess(cmDuration testTimeOut, bool explicitTimeout,
                    std::vector<std::string>* environment,
+                   std::vector<std::string>* environment_modification,
                    std::vector<size_t>* affinity);
   void WriteLogOutputTop(size_t completed, size_t total);
   // Run post processing of the process output for MemCheck