Note that using pkg-config is NOT recommended because of:
1. It doesn't know which language you are using, so language-specific
options such as -std=c++11 or -std=c99 cannot be passed along. Yet,
the build will corrupt if you don't get these correct.
2. It has no means of communicating which defines that should be set
in config.h, effectively disabling them all, possibly leading to
inconsistencies between the library and the executable.
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