adopted to the enforced changes by root 6.18.00.

src/external/libZFRelaxation/CMakeLists.txt

@@ -3,17 +3,20 @@
 #--- generate necessary dictionaries ------------------------------------------
 set(MUSRFIT_INC ${CMAKE_SOURCE_DIR}/src/include)
 set(BMW_TOOLS_INC ${CMAKE_SOURCE_DIR}/src/external/BMWtools)
-set(PREFIX_INC ${CMAKE_INSTALL_PREFIX}/include)
+# ROOT requires that the dictonary header files are found at configuration time.
+# Hence, target_include_directories cannot be used here because, targets are 
+# setup only afterwards.
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 
 root_generate_dictionary(
   ZFRelaxationDict 
-  -I${FFTW3_INCLUDE_DIR} 
-  -I${MUSRFIT_INC}
-  -I${BMW_TOOLS_INC}
-  -I${PREFIX_INC}
   ZFRelaxation.h
+  OPTIONS 
+    -I${FFTW3_INCLUDE_DIR} 
+    -I${MUSRFIT_INC}
+    -I${BMW_TOOLS_INC}
+    -inlineInputHeader
   LINKDEF ZFRelaxationLinkDef.h
-  OPTIONS -inlineInputHeader
   MODULE ZFRelaxation
 )