[T-242] Docker for alpine and centos binaries

[DeMoorJasper]

This PR aims to create binaries for alpine and linux versions that use an older libc than the one we use in CI (apparently centos is a good target to build against as it's using a very old libc version... source: prebuild)

Using docker this PR virtualises centos and alpine using the docker images by the prebuild project.

Related #23 #18
Closes T-242

[mischnic]

• The alpine issue: Alpine uses musl, which is a reimplementation of glibc. It seems like the fts functions (which are part of glibc) aren't installed by default. They can be installed with apk add fts-dev (which should install the fts package as well?), which should hopefully fix the error.

• The centos problem:
  64-bit support for fts was only added in glibc 2.23: https://abi-laboratory.pro/?view=changelog&l=glibc&v=2.23
  Not quite sure what we can/should do here

[DeMoorJasper]

@mischnic awesome, thanks for the fast review.

Knew alpine ran musl didn't know you needed to install that package, appears to have fixed it. Thanks!

Read about centos only supporting 32bit fts, that's what I meant with superold. Didn't even know 32-bit was still a thing. Have no clue if it's possible to build 2 versions and just switch between 32 and 64 bit fts.

[mischnic]

prebuild might support fallback to 32bit, but having libraries with different architectures can cause problems on linux: if the 32bit watcher library links dynamically to glibc, then glibc needs to be installed in a 32bit variant as well (and Node at runtime needs to likely be 32 bit as well). I'm not sure how this works out on centos.

[mischnic]

Another possibility: loading glibc via dlopen, so that we can handle a failure ourselves and fallback to the BruteForceBackend.

[DeMoorJasper]

Isn't it used for the BruteForceBackend?

[mischnic]

What do you mean?

[DeMoorJasper]

@mischnic I mean it's used for BruteForceBackend::readTree on unix based systems (mac and linux)

So we can't really fallback to BruteForceBackend as this is already used for the BruteForceBackend

[mischnic]

Ah, you're right

[DeMoorJasper]

Rewrote the readDirTree to support centos without needing fts

implementation	runtime
fts	600ms
custom	700ms

[height]

The task T-242 has been marked as "Done".