[PATCH] kexec/zstd: fix static zstd build

[Simon Horman]

On Sun, Jun 22, 2025 at 06:12:53AM -0700, Nicholas Sielicki wrote:
> 60ce9bdf introduced a local reimplementation of ZSTD_isFrame to this
> tree, as the definition in libzstd is only available for static linking.
> When a static build of libzstd is in-fact available to kexec-tools, this
> was previously causing multiple-definition errors at link time.
> 
> prefer the ZSTD_isFrame from libzstd, if it's available, by adding
> __attribute__((weak)) on the local definition.
> 
> Signed-off-by: Nicholas Sielicki <opensource at nslick.com>

Thanks, applied.