Revert "compiler-rt: use __GLIBC_PREREQ for SANITIZER_INTERCEPT_GETRANDOM"
Revert "compiler-rt: move all __GLIBC_PREREQ into own header file"

"move all __GLIBC_PREREQ" breaks build on some bots

This reverts commit 2d75ee937397c209dbd95aefc88da6301fed07da.
This reverts commit 7a6461fcc2ed8e28c43993c561721af0bbe97f3a.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@373367 91177308-0d34-0410-b5e6-96231b3b80d8