fix versionlock grep command failing

cta-release/CMakeLists.txt

@@ -57,7 +57,7 @@ safedl("https://yum.oracle.com/RPM-GPG-KEY-oracle-ol${OSV}"
 
 # generate versionlock file
 execute_process(
-    COMMAND grep "%package" ../cta.spec.in
+    COMMAND grep "%package" ${CMAKE_CURRENT_SOURCE_DIR}/../cta.spec.in
     COMMAND awk "{print $3}"
     COMMAND grep -v "cta-release"
     OUTPUT_VARIABLE RESULT OUTPUT_STRIP_TRAILING_WHITESPACE