code-coverage: Bugfix for branch coverage
    
 - Missing dash for this option on lcov.
    
    Signed-off-by: Saul Romero <saul.romero@arm.com>

diff --git a/coverage-tool/coverage-reporting/merge.py b/coverage-tool/coverage-reporting/merge.py
index bb07b10..933f6de 100755
--- a/coverage-tool/coverage-reporting/merge.py
+++ b/coverage-tool/coverage-reporting/merge.py
@@ -197,7 +197,7 @@
 # Exploit LCOV merging capabilities
 # Example of LCOV usage: lcov -rc lcov_branch_coverage=1 -a coverage_1.info \
 # -a coverage_2.info -o coverage_merge.info
-command = ['lcov', '-rc', 'lcov_branch_coverage=1']
+command = ['lcov', '--rc', 'lcov_branch_coverage=1']
 
 for file_name in info_files_to_merge:
     command.append('-a')