try to find pcre.h for HAVE_RULES in any case (#3185)

Author: DGarry82

cmake/findDependencies.cmake

@@ -7,9 +7,12 @@ if (BUILD_GUI)
 endif()
 
 if (HAVE_RULES)
+    find_path(PCRE_INCLUDE pcre.h)
     find_library(PCRE_LIBRARY pcre)
-    if (NOT PCRE_LIBRARY)
+    if (NOT PCRE_LIBRARY OR NOT PCRE_INCLUDE)
         message(FATAL_ERROR "pcre dependency for RULES has not been found")
+    else()
+        include_directories(${PCRE_INCLUDE})
     endif()
 endif()