Reducing build times of ldc-build-runtime

[Jacob Carlborg]

I'm working on the CI setup for iOS using Bitrise [1]. I'm currently 
hitting the 45 min build time limit. It takes around 11 minutes for 
building LDC itself and then running `ldc-build-runtime` times out, so 
I'm guessing it takes more than 34 minutes. The last completed object 
file is at the progress: 847/896, so it's almost complete.

Is there a way to reduce the build times? It looks like it compiles all 
files separately. Is it possible to compile multiple files at once? 
Perhaps that could reduce the build times. It also seems that there are 
four versions built: regular, debug, unittest and unittest-debug. Are 
all necessary? Can we avoid building some version(s)? Perhaps skip 
unittest and only build unittest-debug?

Since this is done using cross-compiling it might be possible to build 
the binaries on a different CI service and then trigger a build on 
Bitrise using their API to run the actual tests. But that would make it 
more complicated.

[1] https://bitrise.io

-- 
/Jacob Carlborg