Add definitions for symbols in unit test for prctl. Follow up to: https://reviews.llvm.org/D122851

[eugenis]

LGTM

compiler-rt/test/sanitizer_common/TestCases/Linux/prctl.cpp

 // RUN: %clangxx %s -o %t && %run %t %p
 
 #include <assert.h>
 #include <errno.h>
 #include <stdint.h>
 #include <sys/prctl.h>
 
+#ifndef PR_SCHED_CORE
+#  define PR_SCHED_CORE 62
+#endif
+
+#ifndef PR_SCHED_CORE_CREATE
+#  define PR_SCHED_CORE_CREATE 1
+#endif
+
 int main() {
 
   int res;
   res = prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, 0, 0, 0);
   if (res < 0) {
     assert(errno == EINVAL);
     return 0;
   }