pkg-config does not find dependencies in library_install_prefix

[swnf]

Problem

In my build scripts, pkg-config could not find the dependencies in library_install_prefix as expected. It seems like pyodide-build tries to configure pkg-config here:

pyodide-build/pyodide_build/buildpkg.py

Lines 552 to 554 in 4805d73

	# Using PKG_CONFIG_LIBDIR instead of PKG_CONFIG_PATH,
	# so pkg-config will not look in the default system directories
	"PKG_CONFIG_LIBDIR": str(self.library_install_prefix / "lib/pkgconfig"),

But in a call to emconfigure ./configure ... emscripten will override this variable.

Proposed solution

I think it is necessary to set EM_PKG_CONFIG_PATH. This can be done in addition to PKG_CONFIG_LIBDIR. I'm unsure if the existing PKG_CONFIG_LIBDIR has any observable effect.

[hoodmane]

Sounds reasonable, PR welcome.

[swnf]

I've created PR #52 for this issue.