Build without thread support

[Lunatix89]

I am using this library in a project which decodes a H264 stream in Javascript / WebAssembly but due to Meltdown and Spectre it is very complicated to use pthread with emscripten in Firefox and Safari (see https://dzone.com/articles/webassembly-threads-in-firefox if you are interested about the topic).

My question is now, since I'm only using the decoder: would it be possible to disable thread support at all?
I've tried building without the "-pthread" flag but I get link errors when linking the "main executable" with emscripten.

error: undefined symbol: pthread_attr_setschedpolicy (referenced by top-level compiled C/C++ code)
warning: Link with `-s LLD_REPORT_UNDEFINED` to get more information on undefined symbols
warning: To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`
warning: _pthread_attr_setschedpolicy may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
error: undefined symbol: pthread_attr_setscope (referenced by top-level compiled C/C++ code)
warning: _pthread_attr_setscope may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
error: undefined symbol: sem_timedwait (referenced by top-level compiled C/C++ code)
warning: _sem_timedwait may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
Error: Aborting compilation due to previous errors
em++: error: '/emsdk/node/12.18.1_64bit/bin/node /emsdk/upstream/emscripten/src/compiler.js /tmp/tmp7yki8dj2.txt' failed (1)

[huili2]

openh264 does not have such kind of thread support scripts. You'd better see how the build script changes the command into openh264 build info.