[poky] Library paths for Makefile based recipes

[Darren Hart]

I'm working on packaging kernelshark ("make gui" for the trace-cmd recipe
basically). It fails trying to link to -lgtk-x11-2.0. I have added gtk+
as a DEPENDS and the library does exist in the sysroots. I have also added
"inherit pkgconfig" as the project Makefile uses it extensively.

gcc trace-view-main.o trace-view.o trace-view-store.o trace-filter.o trace-compat.o trace-hash.o libtracecmd.a -rdynamic -o trace-view -pthread -lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lgio-2.0 -lpangoft2-1.0 -lgdk_pixbuf-2.0 -lpangocairo-1.0 -lcairo -lpango-1.0 -lfreetype -lfontconfig -lgobject-2.0 -lgmodule-2.0 -lgthread-2.0 -lrt -lglib-2.0   -L. -ltracecmd -ldl
| /usr/bin/ld: cannot find -lgtk-x11-2.0
| collect2: ld returned 1 exit status
| make[1]: *** [trace-view] Error 1
| make[1]: *** Waiting for unfinished jobs....
| make: *** [gui] Error 2
| FATAL: oe_runmake failed
| ERROR: Task failed: ('function do_compile failed', '/vol/1/dvhart/poky.git/build/tmp/work/core2-poky-linux/kernelshark-1.0.4+git0+0d252224626bd6926324f023a65f20c165232891-r0/temp/log.do_compile.12830')
NOTE: package kernelshark-1.0.4+git0+0d252224626bd6926324f023a65f20c165232891-r0: task do_compile: Failed
ERROR: Task 8 (/home/dvhart/data/poky.git/meta/recipes-kernel/trace-cmd/kernelshark_git.bb, do_compile) failed with 1
ERROR: '/home/dvhart/data/poky.git/meta/recipes-kernel/trace-cmd/kernelshark_git.bb' failed

Without the "gui" target, trace-cmd doesn't link against anything outside of
libc and ld, so the original recipe doesn't run into this.

How does bitbake try to make the library path available to a make based
project? I've tried various incantations from other non-autotools gtk+
based recipes:

do_compile_prepend = " \
        export LDFLAGS='${LDFLAGS} `${STAGING_BINDIR_NATIVE}/pkg-config gtk+-2.0 --libs`'; \
       export CFLAGS='${CFLAGS} -I./ `${STAGING_BINDIR_NATIVE}/pkg-config gtk+-2.0 --cflags`'; "

export VERBOSE=1
CFLAGS += "-L ${STAGING_LIBDIR}"
LDFLAGS += "-L ${STAGING_LIBDIR}"
CFLAGS_prepend = "-L ${STAGING_LIBDIR}"
LDFLAGS_prepend = "-L ${STAGING_LIBDIR}"

However, these don't appear to impact the commands executed by the project
Makefile (despite the fact that it tries to import existing CFLAGS).

-- 
Darren Hart
Yocto Linux Kernel