cmake: set cmake policy CMP0060 to NEW

Link libraries by full path even in implicit directories:
https://cmake.org/cmake/help/v3.5/policy/CMP0060.html

This fixes a linker error with CMake 3.5, which as a result of

    target_link_libraries(orocos-rtt-${OROCOS_TARGET}_dynamic /full/path/to/liblog4cpp.so)

adds

    -llog4cpp

to the linker command line, which results in a linker error:

/usr/bin/ld: cannot find -llog4cpp

Not sure why the install-space is considered as an implicit link directory by CMake.

Signed-off-by: Johannes Meyer <[email protected]>

CMakeLists.txt

@@ -3,16 +3,24 @@
 #
 CMAKE_MINIMUM_REQUIRED(VERSION 2.6.0)
 
-# for CMake 2.6 corrected behaviour (see "cmake --help-policy CMP0003")
+# CMP0003: Libraries linked via full path no longer produce linker search paths
+# (see "cmake --help-policy CMP0003")
 IF(POLICY CMP0003)
   CMAKE_POLICY(SET CMP0003 NEW)
 ENDIF(POLICY CMP0003)
 
-# Suppress cmake policy warning in included rtt_macros.cmake file in CMake >= 3.0.2 (see "cmake --help-policy CMP0026")
+# CMP0026: Suppress cmake policy warning in included rtt_macros.cmake file (CMake >= 3.0.2)
+# (see "cmake --help-policy CMP0026")
 if(POLICY CMP0026)
   cmake_policy(SET CMP0026 OLD)
 endif()
 
+# CMP0060: Link libraries by full path even in implicit directories (CMake >= 3.3)
+# (see "cmake --help-policy CMP0060")
+IF(POLICY CMP0060)
+  CMAKE_POLICY(SET CMP0060 NEW)
+ENDIF(POLICY CMP0060)
+
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