CPack add necessary check to detect/warns/error on ABSOLUTE DESTINATION

The [usually] wrong usage of absolute DESTINATION in INSTALL rules
keeps popping-up on the ML. We shall have some way to:
  1) easily detect it.
  2) forbids this for some CPack generator like NSIS
In fact it should certainly be forbidden for *any* generators
when used on Windows but we may implements that on top of the current
patch.
The patch ask the task to the generated cmake_install.cmake scripts.
Those scripts are a little bit more complicated with that but
iff there are absolute DESTINATION. This cost nothing if relative
DESTINATION are used.
Two new vars are introduced (and documented to handle that):
CPACK_WARN_ON_ABSOLUTE_INSTALL_DESTINATION
and
CPACK_ERROR_ON_ABSOLUTE_INSTALL_DESTINATION

1 files changed, 6 insertions, 0 deletions

diff --git a/Source/CPack/cmCPackNSISGenerator.cxx b/Source/CPack/cmCPackNSISGenerator.cxx
index 63189de..481fd2b 100644
--- a/Source/CPack/cmCPackNSISGenerator.cxx
+++ b/Source/CPack/cmCPackNSISGenerator.cxx
@@ -639,6 +639,12 @@ cmCPackNSISGenerator::SupportsSetDestdir() const
 }
 
 //----------------------------------------------------------------------
+bool cmCPackNSISGenerator::SupportsAbsoluteDestination() const
+{
+        return false;
+}
+
+//----------------------------------------------------------------------
 bool cmCPackNSISGenerator::SupportsComponentInstallation() const
 {
         return true;