fix(dracut-install): do not try to copy files from the root directory

HWCAP library path needs at least two parent directories, for example:

/lib64/power6x/libc.so.6
/lib64/glibc-hwcaps/power9/libpthread-2.28.so (glibc 2.33+)

Before:

dracut-install: Lib install: '/lib64/libz.so.1'
dracut-install: dracut_install('/lib64/libz.so', '/lib64/libz.so', 0, 0, 1)
dracut-install: dracut_install('//libz.so.1', '//libz.so.1', 0, 0, 1)
dracut-install: dracut_install('//libz.so', '//libz.so', 0, 0, 1)

After:

dracut-install: Lib install: '/lib64/libz.so.1'
dracut-install: dracut_install('/lib64/libz.so', '/lib64/libz.so', 0, 0, 1)

src/install/dracut-install.c

@@ -392,7 +392,8 @@ static int library_install(const char *src, const char *lib)
                 return ret;
 
         ppdir = dirname_malloc(pdir);
-        if (!ppdir)
+        /* only one parent directory, not HWCAP library */
+        if (!ppdir || streq(ppdir, "/"))
                 return ret;
 
         pppdir = dirname_malloc(ppdir);