Disable znver1 by default

This crap won't be upstreamized and we do not have so many resources
to build and test yet another pack of binaries without big performance gain.

rpm-software-management#1035 (comment)

To enable automatic detection of Ryzen CPUs create a file
/etc/rpm/znver1_enable

lib/rpmrc.c

@@ -959,6 +959,11 @@ static int is_geode(void)
 
 #if defined(__linux__) && (defined(__i386__) || defined(__x86_64__))
 static int is_ryzen() {
+    // Disable this crap by default on ROSA.
+    // rpmExpandNumeric does not work here for some reasons,
+    // probably this is done earlier than macros are loaded.
+    if (access("/etc/rpm/znver1_enable", F_OK) != 0)
+        return 0;
     uint32_t eax, ebx, ecx, edx;
     char vendor[13];
     int family;