fuzzers: use -fsanitizer=fuzzer if clang supports it

Closes systemd/systemd#10645

meson.build

@@ -353,7 +353,6 @@ substs.set('VARLOGDIR',                                       varlogdir)
 # substs.set('MEMORY_ACCOUNTING_DEFAULT',                       memory_accounting_default ? 'yes' : 'no')
 #endif // 0
 substs.set('HIGH_RLIMIT_NOFILE',                              conf.get('HIGH_RLIMIT_NOFILE'))
-substs.set('BUILD_ROOT',                                      meson.current_build_dir())
 
 #####################################################################
 
@@ -375,7 +374,14 @@ install_tests = get_option('install-tests')
 # endif
 #
 # if want_libfuzzer
-#         fuzzing_engine = meson.get_compiler('cpp').find_library('Fuzzer')
+#         fuzzing_engine = meson.get_compiler('cpp').find_library('Fuzzer', required : false)
+#         if fuzzing_engine.found()
+#                 add_project_arguments('-fsanitize-coverage=trace-pc-guard,trace-cmp', language : 'c')
+#         elif cc.has_argument('-fsanitize=fuzzer-no-link')
+#                 add_project_arguments('-fsanitize=fuzzer-no-link', language : 'c')
+#         else
+#                 error('Looks like neither libFuzzer nor -fsanitize=fuzzer-no-link is supported')
+#         endif
 # elif want_ossfuzz
 #         fuzzing_engine = meson.get_compiler('cpp').find_library('FuzzingEngine')
 # elif want_fuzzbuzz
@@ -3199,9 +3205,16 @@ endforeach
 #         dependencies = tuple[2]
 #         defs = tuple.length() >= 4 ? tuple[3] : []
 #         incs = tuple.length() >= 5 ? tuple[4] : includes
+#         link_args = []
 #
-#         if fuzzer_build
+#         if want_ossfuzz or want_fuzzbuzz
 #                 dependencies += fuzzing_engine
+#         elif want_libfuzzer
+#                 if fuzzing_engine.found()
+#                         dependencies += fuzzing_engine
+#                 else
+#                         link_args += ['-fsanitize=fuzzer']
+#                 endif
 #         else
 #                 sources += 'src/fuzz/fuzz-main.c'
 #         endif
@@ -3219,6 +3232,7 @@ endforeach
 #                 link_with : link_with,
 #                 dependencies : dependencies,
 #                 c_args : defs,
+#                 link_args: link_args,
 #                 install : false)
 # endforeach
 # endif