unset CMAKE_BUILD_TYPE when WITH_COVERAGE = ON (#18541)

install coverage package in develop image
test = develop

Dockerfile

@@ -125,6 +125,12 @@ RUN pip3.6 --no-cache-dir install pylint pytest astroid isort
 RUN pip3.7 --no-cache-dir install pylint pytest astroid isort
 RUN pip --no-cache-dir install pylint pytest astroid isort LinkChecker
 
+# for coverage
+RUN pip3 --no-cache-dir install coverage
+RUN pip3.6 --no-cache-dir install coverage
+RUN pip3.7 --no-cache-dir install coverage
+RUN pip --no-cache-dir install coverage
+
 COPY ./python/requirements.txt /root/
 RUN pip3 --no-cache-dir install -r /root/requirements.txt
 RUN pip3.6 --no-cache-dir install -r /root/requirements.txt

cmake/coveralls.cmake

@@ -62,7 +62,6 @@ function(code_coverage _COVERAGE_SRCS _COVERALLS_UPLOAD _CMAKE_SCRIPT_PATH)
 endfunction()
 
 if(WITH_COVERAGE)
-    set(CMAKE_BUILD_TYPE "Debug")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -O0 -fprofile-arcs -ftest-coverage")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g -O0 -fprofile-arcs -ftest-coverage")