I did some initial work regarding this topic
I made sure one can compile libosmocore with following toolchain (I had to apply similar toolchain patches that appear in the wiki page too):
https://osmocom.org/projects/baseband/wiki/GnuArmToolchain
I then used following flags to build libosmocore (as seen in osmocombb Makefile):
opt_enable="--disable-doxygen --host=arm-none-eabi --enable-embedded --disable-shared --disable-tests ac_cv_header_sys_select_h=no --disable-tests ac_cv_header_sys_socket_h=no"
export CFLAGS="-Os -ffunction-sections -I$(TOPDIR)/target/firmware/include -nostartfiles -nodefaultlibs"
I then modified osmocomBB Makefile to use libosmocore.a from a different directory, defining a new LIBOSMOCORE_PREFIX automake variable which can be used to point to it.
I could compile the firmware (make -C target/firmware CROSS_COMPILE=arm-none-eabi-) but it still fails at linking stage iwth some minor lining issues which still needs to be resolved.
I attach a patch with changes I did in osmocomBB so far.
lib/libosmocore.a(msgb.o): In function `msgb_alloc':
git/libosmocore/src/msgb.c:82: undefined reference to `talloc_named_const'
lib/libosmocore.a(logging.o): In function `const_basename':
git/libosmocore/src/logging.c:317: undefined reference to `strrchr'
lib/libosmocore.a(logging.o): In function `assert_loginfo':
git/libosmocore/src/logging.c:177: undefined reference to `fprintf'
git/libosmocore/src/logging.c:181: undefined reference to `_impure_ptr'
lib/libosmocore.a(logging.o): In function `_output':
git/libosmocore/src/logging.c:359: undefined reference to `time'
git/libosmocore/src/logging.c:360: undefined reference to `ctime'
make: *** [Makefile.inc:135: board/compal_e88/hello_world.highram.elf] Error 1
talloc_named_const is proobably still missing in libosmocore
pseudotalloc.
