Revert "[roottest] Remove sequential compilation with Ninja."

This reverts commit e8519e4.

Since a week, I experienced several corrupted incremental builds
and tests. I strongly suspect this commit to be the reason. Indeed
launching Ninja concurrently that need to build a dependency will
execute the same command multiple times, leading to potentially
corrupted files. In principle, the same problem applies to Makefiles
but there we use the /fast targets and ignore outdated dependencies.

Author: hahnjo

roottest/cmake/modules/RoottestMacros.cmake

@@ -264,6 +264,9 @@ macro(ROOTTEST_COMPILE_MACRO filename)
     set_property(TEST ${COMPILE_MACRO_TEST} PROPERTY FAIL_REGULAR_EXPRESSION "Warning in")
   endif()
   set_property(TEST ${COMPILE_MACRO_TEST} PROPERTY ENVIRONMENT ${ROOTTEST_ENVIRONMENT})
+  if(CMAKE_GENERATOR MATCHES Ninja AND NOT MSVC)
+    set_property(TEST ${COMPILE_MACRO_TEST} PROPERTY RUN_SERIAL true)
+  endif()
   if (ARG_FIXTURES_SETUP)
     set_property(TEST ${COMPILE_MACRO_TEST} PROPERTY
       FIXTURES_SETUP ${ARG_FIXTURES_SETUP})
@@ -367,6 +370,9 @@ macro(ROOTTEST_GENERATE_DICTIONARY dictname)
                                     -- ${always-make})
 
   set_property(TEST ${GENERATE_DICTIONARY_TEST} PROPERTY ENVIRONMENT ${ROOTTEST_ENVIRONMENT})
+  if(CMAKE_GENERATOR MATCHES Ninja AND NOT MSVC)
+    set_property(TEST ${GENERATE_DICTIONARY_TEST} PROPERTY RUN_SERIAL true)
+  endif()
 
   if (ARG_FIXTURES_SETUP)
     set_property(TEST ${GENERATE_DICTIONARY_TEST} PROPERTY
@@ -481,6 +487,9 @@ macro(ROOTTEST_GENERATE_REFLEX_DICTIONARY dictionary)
                                     -- ${always-make})
 
   set_property(TEST ${GENERATE_REFLEX_TEST} PROPERTY ENVIRONMENT ${ROOTTEST_ENVIRONMENT})
+  if(CMAKE_GENERATOR MATCHES Ninja AND NOT MSVC)
+    set_property(TEST ${GENERATE_REFLEX_TEST} PROPERTY RUN_SERIAL true)
+  endif()
 
   if (ARG_FIXTURES_SETUP)
     set_property(TEST ${GENERATE_REFLEX_TEST} PROPERTY
@@ -600,6 +609,10 @@ macro(ROOTTEST_GENERATE_EXECUTABLE executable)
       RESOURCE_LOCK ${ARG_RESOURCE_LOCK})
   endif()
 
+  if(CMAKE_GENERATOR MATCHES Ninja AND NOT MSVC)
+    set_property(TEST ${GENERATE_EXECUTABLE_TEST} PROPERTY RUN_SERIAL true)
+  endif()
+
   if(MSVC AND NOT CMAKE_GENERATOR MATCHES Ninja)
     add_custom_command(TARGET ${executable} POST_BUILD
        COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG>/${executable}.exe