liblcf tests do not compile on fedora 30

[carstene1ns]

[  375s] + cd liblcf-0.6.2
[  375s] + make check
[  375s] make  test_runner
[  375s] make[1]: Entering directory '/home/abuild/rpmbuild/BUILD/liblcf-0.6.2'
[  375s]   CXX      tests/test_runner-time_stamp.o
[  377s]   CXX      tests/test_runner-flag_set.o
[  378s]   CXX      tests/test_runner-test_main.o
[  379s] In file included from tests/test_main.cpp:11:
[  379s] tests/doctest.h: In member function 'int doctest::Context::run()':
[  379s] tests/doctest.h:5899:9: error: expected identifier before '{' token
[  379s]  5899 |         { std::cout << std::string(); };
[  379s]       |         ^
[  379s] tests/doctest.h:5899:9: error: type-specifier invalid in lambda
[  379s] make[1]: *** [Makefile:1950: tests/test_runner-test_main.o] Error 1
[  379s] make[1]: Leaving directory '/home/abuild/rpmbuild/BUILD/liblcf-0.6.2'
[  379s] make: *** [Makefile:2279: check-am] Error 2
[  379s] error: Bad exit status from /var/tmp/rpm-tmp.ibq5Jf (%check)

update doctest?

[fdelapena]

Fedora 30 is end of life, likely not worth if 31 and later work as expected.

[carstene1ns]

Closing as this vanishes. Fedora after 31 does not get any package updates from here anyway, since we have downstream builds now.