Use __gcov_dump and __gcov_reset in execv and fork context.

	PR gcov-profile/93623
	* libgcov-interface.c (__gcov_fork): Do not flush
	and reset only in child process.
	(__gcov_execl): Dump counters only and reset them
	only if exec* fails.
	(__gcov_execlp): Likewise.
	(__gcov_execle): Likewise.
	(__gcov_execv): Likewise.
	(__gcov_execvp): Likewise.
	(__gcov_execve): Likewise.