We should avoid testing on Skylake CPUs because QEMU TCG is broken for Skylake

Makefile

@@ -17,8 +17,14 @@ all:
 	patch -Np1 -d libguestfs-1.42.0 < libguestfs-1.42.0-fix_test_timeout.patch
 	cd libguestfs-1.42.0 && ./configure --prefix=/usr --sysconfdir=/etc --with-extra-packages="glibc readline ncurses util-linux xz pcre zlib systemd iproute2 libcap jansson augeas hivex libtirpc parted mdadm libaio cryptsetup popt openssl json-c cdrkit gptfdisk gcc"
 	$(MAKE) -C libguestfs-1.42.0
-	chown -Rv nobody libguestfs-1.42.0
-	su nobody -s /bin/bash -c "PATH=$$PATH SKIP_QEMU_FORCE_TCG_SH=1 make -C libguestfs-1.42.0 check"
+
+# As of November 2020 QEMU 5.1.0 does not have functioning TCG implementation of Skylake CPU - attempt to run libguestfs tests in TCG mode bound to fail on Skylake system.
+# Let's skip testing (with heavy heart) hoping that whatever bugs lurking around will become apparent during builds for other types of CPUs.
+# This condition should be removed in the future when QEMU TCG will catch up with real world Skylake CPU.
+	if [[ `lscpu | grep -c "^Model name:.*Skylake"` = 0 ]] ; then \
+	    chown -Rv nobody libguestfs-1.42.0 ; \
+	    su nobody -s /bin/bash -c "PATH=$$PATH SKIP_QEMU_FORCE_TCG_SH=1 make -C libguestfs-1.42.0 check" ; \
+	fi
 	$(MAKE) -C libguestfs-1.42.0 install REALLY_INSTALL=yes
 	rm -rf libguestfs-1.42.0