Fix krb5 detection without pkgconfig file.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit 1b466c3d2b)

ConfigureChecks.cmake

@@ -43,5 +43,24 @@ endif( )
 
 pkg_search_module( KRB5 krb5 )
 if( NOT KRB5_FOUND)
-  tde_message_fatal( "krb5 library is required but not found on your system" )
+  if( NOT DEFINED KRB5_CONFIG_EXECUTABLE )
+    find_program( KRB5_CONFIG_EXECUTABLE NAMES krb5-config )
+    if( NOT KRB5_CONFIG_EXECUTABLE )
+      tde_message_fatal( "krb5 library is required but not found on your system" )
+    endif( )
+  endif( )
+
+  execute_process(
+    COMMAND ${KRB5_CONFIG_EXECUTABLE} --libs
+    OUTPUT_VARIABLE KRB5_LIBRARIES
+    ERROR_VARIABLE KRB5_LIBRARIES
+  )
+  execute_process(
+    COMMAND ${KRB5_CONFIG_EXECUTABLE} --cflags
+    OUTPUT_VARIABLE KRB5_INCLUDE_DIRS
+    ERROR_VARIABLE KRB5_INCLUDE_DIRS
+  )
+  if( NOT "${KRB5_LIBRARIES}" STREQUAL "" )
+    set( KRB5_FOUND 1 )
+  endif( )
 endif( )