MDEV-34942 packaging dependency for eigen3

make build_depends.cmake resolve directories too

cmake/build_depends.cmake

@@ -2,7 +2,7 @@ IF(RPM)
   MACRO(FIND_DEP V)
     SET(out ${V}_DEP)
     IF (NOT DEFINED ${out})
-      IF(EXISTS ${${V}} AND NOT IS_DIRECTORY ${${V}})
+      IF(EXISTS ${${V}})
         EXECUTE_PROCESS(COMMAND ${ARGN} RESULT_VARIABLE res OUTPUT_VARIABLE O OUTPUT_STRIP_TRAILING_WHITESPACE)
       ELSE()
         SET(res 1)
@@ -30,7 +30,7 @@ IF(RPM)
       FIND_LIBRARY(${V} ${L})
     ENDIF()
     GET_PROPERTY(T CACHE ${V} PROPERTY TYPE)
-    IF ((T STREQUAL FILEPATH OR V MATCHES "^CMAKE_COMMAND$") AND ${V} MATCHES "^/")
+    IF ((T MATCHES "PATH$" OR V MATCHES "^CMAKE_COMMAND$") AND ${V} MATCHES "^/")
       IF (RPM)
         FIND_DEP(${V} rpm -q --qf "%{NAME}" -f ${${V}})
       ELSE() # must be DEB