How to assign gcc toolchain to snapcraft

snap
1

log info shows snapcraft try to install gcc5 for itself .if i need newer gcc.because i get err

LD spl/u-boot-spl
arm-linux-gnueabihf-ld.bfd: u-boot-spl: Not enough room for program headers, try linking with -N
arm-linux-gnueabihf-ld.bfd: final link failed: Bad value
make[1]: *** [spl/u-boot-spl] Error 1
make: *** [spl/u-boot-spl] Error 2
Failed to run ‘build’: Exit code was 2.

and i found below that snapcraft use gcc5 not gcc6 i install.how to assign gcc6 to snapcraft

DEPRECATED: The ‘prepare’ keyword has been replaced by ‘override-build’
See http://snapcraft.io/docs/deprecation-notices/dn7 for more information.
DEPRECATED: The ‘build’ keyword has been replaced by ‘override-build’
See http://snapcraft.io/docs/deprecation-notices/dn8 for more information.
DEPRECATED: The ‘install’ keyword has been replaced by ‘override-build’
See http://snapcraft.io/docs/deprecation-notices/dn9 for more information.
Installing build dependencies: binutils-arm-linux-gnueabihf build-essential dpkg-dev g++ g+±5 gcc gcc-5 gcc-5-arm-linux-gnueabihf gcc-arm-linux-gnueabihf
Reading package lists… Done
Building dependency tree
Reading state information… Done
Suggested packages:
binutils-doc debian-keyring g+±multilib g+±5-multilib gcc-5-doc libstdc++6-5-dbg gcc-multilib libtool gcc-doc gcc-5-multilib gcc-5-locales
libgcc1-dbg libgomp1-dbg libitm1-dbg libatomic1-dbg libasan2-dbg liblsan0-dbg libtsan0-dbg libubsan0-dbg libcilkrts5-dbg libmpx0-dbg
libquadmath0-dbg gcc-5-multilib-arm-linux-gnueabihf libgcc1-dbg-armhf-cross libgomp1-dbg-armhf-cross libitm1-dbg-armhf-cross
libatomic1-dbg-armhf-cross libasan2-dbg-armhf-cross liblsan0-dbg-armhf-cross libtsan0-dbg-armhf-cross libubsan0-dbg-armhf-cross
libcilkrts5-dbg-armhf-cross libmpx0-dbg-armhf-cross libquadmath0-dbg-armhf-cross gdb-arm-linux-gnueabihf
The following NEW packages will be installed:
binutils-arm-linux-gnueabihf build-essential dpkg-dev g++ g+±5 gcc gcc-5 gcc-5-arm-linux-gnueabihf gcc-arm-linux-gnueabihf
0 upgraded, 9 newly installed, 0 to remove and 91 not upgraded.
Need to get 17.3 MB/26.4 MB of archives.
After this operation, 82.3 MB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 gcc-5 amd64 5.4.0-6ubuntu1~16.04.10 [8,426 kB]

2

Well, snapcraft does not need to use deb packages at all when building.

Though one way around a too old gcc in uboot builds is to simply build on a newer release that actually has the wanted gcc … (typically a gadget only contains the bootloader binary and no stage-packages so the distro you build on doesn’t actually matter) but you can also just use a linaro toolchain that you download during build… that said, i havent found native ones as tarballs, so only cross building the gadget (using --target-arch=armhf) will work.

Here is a slightly hackish (but working) example:

https://github.com/ogra1/nanopi-air-gadget/blob/master/snapcraft.yaml

(note that this is a bit outdated, instead of prepare it should use the new build-override keyword and such for the special hackery)