dracut-install should parse AT_PLATFORM and AT_HWCAP

[haraldh]

❯ LD_SHOW_AUXV="" ldd /bin/bash | fgrep AT_PLATFORM
AT_PLATFORM:          x86_64
AT_PLATFORM:          x86_64

AT_PLATFORM together with AT_HWCAP should give information on what libraries to install additionally in generic images.

# ldconfig -p|grep -F libc.so
libc.so.6 (libc6,64bit, hwcap: 0x0000001000000000, OS ABI: Linux 2.6.32) => /lib64/power6/libc.so.6
libc.so.6 (libc6,64bit, hwcap: 0x0000000000000200, OS ABI: Linux 2.6.32) => /lib64/power6x/libc.so.6
libc.so.6 (libc6,64bit, OS ABI: Linux 2.6.32) => /lib64/libc.so.6

[fweimer-rh]

We have received a different suggestion downstream: always use the generic library. There is a kludge that handles legacy hwcaps subdirectories:

/* Also try to install the same library from one directory above.
   This fixes the case, where only the HWCAP lib would be installed
   # ldconfig -p|grep -F libc.so
   libc.so.6 (libc6,64bit, hwcap: 0x0000001000000000, OS ABI: Linux 2.6.32) => /lib64/power6/libc.so.6
   libc.so.6 (libc6,64bit, hwcap: 0x0000000000000200, OS ABI: Linux 2.6.32) => /lib64/power6x/libc.so.6
   libc.so.6 (libc6,64bit, OS ABI: Linux 2.6.32) => /lib64/libc.so.6
 */

But it does not work for glibc-hwcaps subdirectories. These are copied into the initramfs as-is, under their glibc-hwcaps paths, for example:

usr/lib64/glibc-hwcaps/power9/libc-2.28.so
usr/lib64/glibc-hwcaps/power9/libm-2.28.so
usr/lib64/glibc-hwcaps/power9/libpthread-2.28.so
usr/lib64/glibc-hwcaps/power9/librt-2.28.so

This causes guest build failures if the hypervisor changes processor feature flags.