toolchain/toolchain-buildroot: glibc 2.32 for ARC needs linux-headers >= 5.1.0

toolchain/toolchain-buildroot: glibc 2.32 for ARC needs linux-headers >= 5.1.0

The ARC support has been merged into glibc 2.32 but it requires
linux-headers >= 5.1.0 [1].

Fixes:
https://gitlab.com/kubu93/toolchains-builder/-/jobs/895774971

[1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=0be8ae3679570ff9a193615a035fc8074a8c704f

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: ARC Maintainers <arc-buildroot@synopsys.com>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>