Bug#51502: building with cmake creates an invalid mysqld_safe.

The problem was incorrect escaping used inside a strnig : in \"$MYSQLD\" was written as "\MYSQL\" 
(backslash and quote characters transposed), when defining FIND_PROC  variable for BSD or SysV
style "ps" command-

Additionally fixed obvious code duplication and random naming in CHECK_PID test.

scripts/CMakeLists.txt

@@ -105,7 +105,7 @@ IF(NOT FIND_PROC)
   EXECUTE_PROCESS(COMMAND ps -uaxww OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE result)
   IF(result MATCHES 0) 
      SET( FIND_PROC
-       "ps -uaxww | grep -v \" grep\" | grep -v mysqld_safe | grep -- "\$MYSQLD\" | grep \" $PID \" > /dev/null")
+        "ps -uaxww | grep -v \" grep\" | grep -v mysqld_safe | grep -- \"$MYSQLD\" | grep \" $PID \" > /dev/null")
   ENDIF()
 ENDIF()
 
@@ -113,20 +113,15 @@ IF(NOT FIND_PROC)
   # SysV style
   EXECUTE_PROCESS(COMMAND ps -ef OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE result)
   IF(result MATCHES 0)
-    SET( FIND_PROC "ps -ef | grep -v \" grep\" | grep -v mysqld_safe | grep -- "\$MYSQLD\" | grep \" $PID \" > /dev/null")
+    SET( FIND_PROC "ps -ef | grep -v \" grep\" | grep -v mysqld_safe | grep -- \"$MYSQLD\" | grep \" $PID \" > /dev/null")
   ENDIF()
 ENDIF()
   
-EXECUTE_PROCESS(COMMAND sh -c "kill -0 $$" OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE result2)
-IF(result3 MATCHES 0)
+EXECUTE_PROCESS(COMMAND sh -c "kill -0 $$" OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE result)
+IF(result MATCHES 0)
   SET(CHECK_PID "kill -0 $PID > /dev/null 2> /dev/null")
 ELSE()
-  EXECUTE_PROCESS(COMMAND sh -c "kill -s 0 $$" OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE result3)
-  IF(result4 MATCHES 0)
-    SET(CHECK_PID "kill -s 0 $PID > /dev/null 2> /dev/null")
-  ELSE()
   SET(CHECK_PID "kill -s SIGCONT $PID  > /dev/null 2> /dev/null")
-  ENDIF()
 ENDIF()
 
 ENDIF(UNIX)