I am building with the ARM 2019.12 external toolchain for an ARM cortex-A7 processor.  When trying to build wpa_supplicant without libopenssl enabled, the build failed with the following errors:

/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_peer/eap_teap.o: in function `eap_teap_decrypt':
eap_teap.c:(.text+0x1af8): undefined reference to `tls_get_tls_unique'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_peer/eap_teap.o: in function `eap_teap_process':
eap_teap.c:(.text+0x2624): undefined reference to `tls_connection_get_cipher_suite'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_common/eap_teap_common.o: in function `eap_teap_derive_eap_msk':
eap_teap_common.c:(.text+0x1a0): undefined reference to `tls_prf_sha256'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_common/eap_teap_common.o: in function `eap_teap_derive_eap_emsk':
eap_teap_common.c:(.text+0x20c): undefined reference to `tls_prf_sha256'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_common/eap_teap_common.o: in function `eap_teap_derive_cmk_basic_pw_auth':
eap_teap_common.c:(.text+0x290): undefined reference to `tls_prf_sha256'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_common/eap_teap_common.o: in function `eap_teap_derive_imck':
eap_teap_common.c:(.text+0x3b8): undefined reference to `tls_prf_sha256'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: eap_teap_common.c:(.text+0x4f4): undefined reference to `tls_prf_sha256'
/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/host/opt/ext-toolchain/bin/../lib/gcc/arm-none-linux-gnueabihf/9.2.1/../../../../arm-none-linux-gnueabihf/bin/ld: ../src/eap_common/eap_teap_common.o:eap_teap_common.c:(.text+0x544): more undefined references to `tls_prf_sha256' follow
collect2: error: ld returned 1 exit status
Makefile:1903: recipe for target 'wpa_supplicant' failed
make[3]: *** [wpa_supplicant] Error 1
package/pkg-generic.mk:266: recipe for target '/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/build/wpa_supplicant-2.9/.stamp_built' failed
make[2]: *** [/home/workspace/PM-04H-Display_buildroot-update/mfgtool-build/build/wpa_supplicant-2.9/.stamp_built] Error 2
Makefile:84: recipe for target '_all' failed
make[1]: *** [_all] Error 2
make[1]: Leaving directory '/home/workspace/PM-04H-Display_buildroot-update/buildroot-2020.05.1'
heldk-4/Makefile:334: recipe for target 'mfgtool' failed
make: *** [mfgtool] Error 1


When the build is tried again with libopenssl enabled, the build completes successfully.  I attached the buildroot configuration that does not have libopenssl enabled that resulted in a failure.  There are several custom external options added that will need to be removed to test building.