Remove link against boost regex library, as normally it is header only when using C++ >= 11.

[Romain-Geissler-1A]

It seems you recently dropped all support for gcc 4.x and C++ < 11 in general, so normally with the compilers you still support the Boost regex library shall be header only. Thus avoid linking against it explicitly.

I didn't test this locally, so let's wait the result of the CI.

[Romain-Geissler-1A]

It looks like this breaks all clang < 4.x tests. How ok is it to remove clang 3.6 to 3.9 from the supported compilers ? Clang 4.0.0 debuted in march 2017, so 6 years ago. The oldest gcc release you still support, gcc 5, debuted in April 2015, so 8 years ago.

[jeremy-murphy]

Thanks for updating this.

I'd like to remove more old compilers from the CI, but I'll just check my notes to see if anyone was actively using them.

[jeremy-murphy]

I just removed Clang 3.x from the Drone config, so please rebase on to the latest develop.

[Romain-Geissler-1A]

Ok I just did, let's see how the CI reacts now ;)

[jeremy-murphy]

Thanks, that's great. The change looks good to me, but I'm not an expert on the b2 build configuration, so I might ask someone else to quickly review it too.

[pdimov]

It doesn't matter whether a library is header-only or not, you still have to link to it, or it won't work.

If this doesn't break CI, then CI doesn't test CMake.

[Romain-Geissler-1A]

Ok, I have reverted the CMakeLists.txt changes.

[Romain-Geissler-1A]

Ping

[jeremy-murphy]

Ping

Sorry, been on holidays!

[jeremy-murphy]

Thanks for improving that!