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, 10 insertions, 1 deletions

diff --git a/Source/CPack/cmCPackGenerator.h b/Source/CPack/cmCPackGenerator.h
index 68ee3f2..ddde8b5 100644
--- a/Source/CPack/cmCPackGenerator.h
+++ b/Source/CPack/cmCPackGenerator.h
@@ -206,13 +206,22 @@ protected:
 
   /**
    * Does the CPack generator support CPACK_SET_DESTDIR?
-   * The default legacy value is 'true' generator
+   * The default legacy value is 'SETDESTDIR_SUPPORTED' generator
    * have to override it in order change this.
    * @return CPackSetDestdirSupport
    */
   virtual enum CPackSetDestdirSupport SupportsSetDestdir() const;
 
   /**
+   * Does the CPack generator support absolute path
+   * in INSTALL DESTINATION?
+   * The default legacy value is 'true' generator
+   * have to override it in order change this.
+   * @return true if supported false otherwise
+   */
+  virtual bool SupportsAbsoluteDestination() const;
+
+  /**
    * Does the CPack generator support component installation?.
    * Some Generators requires the user to set
    * CPACK_<GENNAME>_COMPONENT_INSTALL in order to make this