Keep metadata when using gc-sections with profile-generate.
Keep metadata when using gc-sections with profile-generate.

When building with profile-generate request that metadata is kept
during the gc_sections call, as this can sometimes strip out profile
data.
This missing information in the prof files can then result in missing
functions when using the profile information.

graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust