Get coverage data explicitly from the binary dir

If the binary directory is completely outside the source directory, then
the .da files will not be found, because the --directory flag for lcov
was pointing into the source directory.

Author: friendlyanon

cmake-init/templates/common/cmake/coverage.cmake

@@ -6,7 +6,7 @@ set(
     COVERAGE_TRACE_COMMAND
     lcov -c -q
     -o "${PROJECT_BINARY_DIR}/coverage.info"
-    -d "${PROJECT_SOURCE_DIR}"
+    -d "${PROJECT_BINARY_DIR}"
     --include "${PROJECT_SOURCE_DIR}/*"
     CACHE STRING
     "; separated command to generate a trace for the 'coverage' target"