https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79885
--- Comment #9 from Jeremy Huddleston Sequoia <jeremyhu at macports dot org> ---
Because of this issue, gcc only builds if we have the DevSDK ("headers at /"
package) installed. That package is being provided as a workaround for any
projects that fail to build without it (and note that GCC is the only project
we are aware of that falls into this category). In some future macOS version,
it will cease to be provided. I strongly encourage you to address this issue
as soon as possible to ensure that GCC continues to build with future versions.
