[profile] Fix iteration over profile data entries

Fix a crash when gathering value profile data on i386 Darwin.

The Darwin linker shrinks sections containing aligned structures when
padding is not explicitly added to the end of the structure. When
iterating over these structures, be sure to not walk past the end of the
section.

No tests added, since running `ninja check-profile` on i386 Darwin is
enough to reproduce the original crash.

llvm-svn: 261683
2 files changed