check.mk: typo

[heitbaum]

Small typo:

also on my bionic container - I have had to create the following symlink to successfully compile.

cd /usr/include; ln -s x86_64-linux-gnu/asm .

references:

• https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92247#c10
• https://blog.csdn.net/yihui8/article/details/8620914