Cannot get pkg-config build flags: environment variable error.

[tomneep]

Description

I'm having a strange problem building projects using the HDF5 metapackage on my Mac.

I have fpm and hdf5 installed with homebrew. If I clone the fpm repo, navigate to fpm/example_packages/metapackage_hdf5 and run fpm build I get

❯ fpm build
<ERROR> *cmd_build* Model error: Cannot get pkg-config build flags: environment variable error.
STOP 1

After digging around a bit I found it occurs here:

fpm/src/fpm_pkg_config.f90

Lines 213 to 218 in f266033

	! Set system flags
	success = set_env('PKG_CONFIG_ALLOW_SYSTEM_CFLAGS',value=merge('1','0',allow_system))
	if (.not.success) then
	call fatal_error(error,'Cannot get pkg-config build flags: environment variable error.')
	return
	end if

If I set the environment variable PKG_CONFIG_ALLOW_SYSTEM_CFLAGS (to anything) then the project builds successfully.

❯ PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=0 fpm build
 + mkdir -p build/dependencies
[  0%]                       main.f90
[ 50%]                       main.f90  done.
[ 50%]               metapackage_hdf5
[100%]               metapackage_hdf5  done.
[100%] Project compiled successfully.

Expected Behaviour

I'd expect the project to build without having to define the PKG_CONFIG_ALLOW_SYSTEM_CFLAGS environment variable.

Version of fpm

0.12.0

Platform and Architecture

MacOS/ARM

Additional Information

No response