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, 16 insertions, 0 deletions

diff --git a/Source/CPack/cmCPackDocumentVariables.cxx b/Source/CPack/cmCPackDocumentVariables.cxx
index d2e3802..b529480 100644
--- a/Source/CPack/cmCPackDocumentVariables.cxx
+++ b/Source/CPack/cmCPackDocumentVariables.cxx
@@ -77,4 +77,20 @@ void cmCPackDocumentVariables::DefineVariables(cmake* cm)
          "which is done right before packaging the files."
          " The script is not called by e.g.: make install.", false,
          "Variables common to all CPack generators");
+
+  cm->DefineProperty
+        ("CPACK_WARN_ON_ABSOLUTE_INSTALL_DESTINATION", cmProperty::VARIABLE,
+         "Ask CPack to warn each time a file with absolute INSTALL"
+         " DESTINATION is encountered.",
+         "", false,
+         "Variables common to all CPack generators");
+
+  cm->DefineProperty
+        ("CPACK_ERROR_ON_ABSOLUTE_INSTALL_DESTINATION", cmProperty::VARIABLE,
+         "Ask CPack to error out as soon as a file with absolute INSTALL"
+         " DESTINATION is encountered",
+         "The fatal error is emitted before the installation of "
+         "the offending file takes place. Some CPack generators, like NSIS,"
+         "enforce this internally.", false,
+         "Variables common to all CPack generators");
 }