Fixes a build race seen after 0.13 upgrade
| /home/pokybuild/yocto-worker/meta-oe/build/build/tmp/work/core2-64-poky-linux/uftrace/0.13-r0/git/cmds/dump.c: In function 'dump_mermaid_footer':
| /home/pokybuild/yocto-worker/meta-oe/build/build/tmp/work/core2-64-poky-linux/uftrace/0.13-r0/git/cmds/dump.c:1347:10: fatal error: utils/mermaid.html.cstr: No such file or directory
| 1347 | #include "utils/mermaid.html.cstr" /* This file is a converted of mermaid.html to one string literal in build-time */
| | ^~~~~~~~~~~~~~~~~~~~~~~~~
| compilation terminated.
| make[1]: *** [Makefile:310: /home/pokybuild/yocto-worker/meta-oe/build/build/tmp/work/core2-64-poky-linux/uftrace/0.13-r0/build/cmds/dump.o] Error 1
Signed-off-by: Khem Raj <raj.khem@gmail.com>