glibc was compiled for tc-12.x with: $ echo "CFLAGS += -fomit-frame-pointer -march=i486 -mtune=i686 -Os -pipe" > configparms
..and for tc-11.x with $ echo "CFLAGS += -march=i486 -mtune=i686 -Os -pipe" > configparms
However, in addition, for glibc in tc-11.x, uname_hack was used to force i486, but could not be used for glibc in tc-12.x because it does not compile for linux-5.x kernels.