backport libc++ fix to formatter

[androm3da]

We should backport this fix to formatter_floating_point because it causes compilation errors on targets where int32_t is not compatible with int.

/cherry-pick e1830f5

[mordante]

Thanks for the backport request!
FYI you could have set the milestone in the PR and request the backporting there. (This works too.)

[llvmbot]

/pull-request #87801