Upgrade our testing systems to use GNU Arm Embedded Toolchain 10.3-2021.07 as the new supported version of `gcc`

[Patater]

[Patater]

I've raised #15007 to move our GitHub actions CI to the new version of GCC.

@saheerb has been working on updating the Jenkins CI.

[LDong-Arm]

It's slightly annoying that Mbed CLI 1 prints

[Warning] @,: Compiler version mismatch: Have 10.3.1; expected version >= 9.0.0 and < 10.0.0

The version range is hardcoded in tools/toolchains/gcc.py which is frozen. As it's just a warning, leaving it as it is probably fine...

[jeromecoutant]

As it's just a warning, leaving it as it is probably fine...

I would prefer to remove warnings
Thx

[rwalton-arm]

It's slightly annoying that Mbed CLI 1 prints

[Warning] @,: Compiler version mismatch: Have 10.3.1; expected version >= 9.0.0 and < 10.0.0

The version range is hardcoded in tools/toolchains/gcc.py which is frozen. As it's just a warning, leaving it as it is probably fine...

I don't think fixing that warning would affect the behaviour of the online build system. We should be OK to fix it without creating a new "tools release" for the online compiler. We could probably ignore the frozen tools check in this instance? @Patater

[LDong-Arm]

Ultimately we encourage users to move away from Mbed CLI 1. But if someone disregards the deprecation and does what the warning says (i.e. downgrades GCC to 9.x), they may encounter issues such as NU_M2354 unable to run due to known issues of the old GCC with Armv8-m.