How to make meson accept that `pkg-config --cflags ` has empty result in case only /usr/include is needed

[Andreas Tille <andreas@an3as.eu>]

Hi,

it seems that if a pkg-config file just has

prefix=/usr
includedir=${prefix}/include
Cflags: -I${includedir}

the call

  pkg-config --cflags libfoo

returns nothing which makes sense.  This is for instance the case for
/usr/lib/*/pkgconfig/pbbam.pc of libpbbam-dev and I think that

$ pkg-config --cflags pbbam

$ echo $?
0

is correct behaviour and return code is 0.  However when I try to build
the new package libblasr[1] against this lib I get:


...
Found pkg-config: /usr/bin/pkg-config (0.29)
Determining dependency 'pbbam' with pkg-config executable '/usr/bin/pkg-config'
Called `/usr/bin/pkg-config --modversion pbbam` -> 0
0.18.0
Called `/usr/bin/pkg-config --cflags pbbam` -> 1


meson.build:52:0: ERROR:  Could not generate cargs for pbbam:


I have no idea why meson considers the normal behaviour as error neither
do I have a clue how to convince meson to accept this argument.

Any help would be welcome

      Andreas.


[1] https://salsa.debian.org/med-team/libblasr

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