trying to fix cmake pb for Michel D

CMakeLists.txt

@@ -624,9 +624,9 @@ if(ENABLE_PETSC)
     list(APPEND EXTERNAL_INCLUDES ${ENV_PETSC_DIR}/${ENV_PETSC_ARCH}/include)
     string(REGEX MATCH "PACKAGES_INCLUDES = [^\n\r]*" PETSC_PACKAGES_INCLUDES
            ${PETSC_VARIABLES})
-    string(REPLACE "PACKAGES_INCLUDES = " "" PETSC_PACKAGES_INCLUDES
-           ${PETSC_PACKAGES_INCLUDES})
     if(PETSC_PACKAGES_INCLUDES)
+      string(REPLACE "PACKAGES_INCLUDES = " "" PETSC_PACKAGES_INCLUDES
+             ${PETSC_PACKAGES_INCLUDES})
       string(REPLACE "-I" "" PETSC_PACKAGES_INCLUDES ${PETSC_PACKAGES_INCLUDES})
       string(REPLACE " " ";" PETSC_PACKAGES_INCLUDES ${PETSC_PACKAGES_INCLUDES})
         foreach(VAR ${PETSC_PACKAGES_INCLUDES})
@@ -654,13 +654,17 @@ if(ENABLE_PETSC)
     list(APPEND EXTERNAL_LIBRARIES ${PETSC_LIBS})
     # find additional libraries to link with
     string(REGEX MATCH "PACKAGES_LIBS = [^\n\r]*" PLIBS ${PETSC_VARIABLES})
-    string(REPLACE "PACKAGES_LIBS = " "" PLIBS ${PLIBS})
-    string(STRIP ${PLIBS} PLIBS)
-    list(APPEND EXTERNAL_LIBRARIES "${PLIBS}")
+    if(PLIBS)
+      string(REPLACE "PACKAGES_LIBS = " "" PLIBS ${PLIBS})
+      string(STRIP ${PLIBS} PLIBS)
+      list(APPEND EXTERNAL_LIBRARIES "${PLIBS}")
+    endif(PLIBS)
     string(REGEX MATCH "PCC_LINKER_LIBS = [^\n\r]*" LLIBS ${PETSC_VARIABLES})
-    string(REPLACE "PCC_LINKER_LIBS = " "" LLIBS ${LLIBS})
-    string(STRIP ${LLIBS} LLIBS)
-    list(APPEND EXTERNAL_LIBRARIES "${LLIBS}")
+    if(LLIBS)
+      string(REPLACE "PCC_LINKER_LIBS = " "" LLIBS ${LLIBS})
+      string(STRIP ${LLIBS} LLIBS)
+      list(APPEND EXTERNAL_LIBRARIES "${LLIBS}")
+    endif(LLIBS)
   endif(EXISTS ${ENV_PETSC_DIR}/${ENV_PETSC_ARCH}/conf/petscvariables)
 endif(ENABLE_PETSC)