I ran "sudo port selfupdate" and now I cannot install any ports without an error

[JulioDavidMartinez]

Here is the log:

System headers do not appear to be installed. Most ports should build correctly, but if you experience problems due to a port depending on system headers, please file a ticket at https://trac.macports.org.
Warning: You can install them as part of the Xcode Command Line Tools package by running `xcode-select --install'.
--->  Computing dependencies for fontforgeError: Unable to determine location of a macOS SDK.
Error: Unable to execute port: can't read "configure.sdkroot": Unable to determine location of a macOS SDK.

It always asks me to install xcode-select --install, I have installed it like 50 times. This line is new since the update:

Unable to execute port: can't read "configure.sdkroot":

I have no idea what file this is nor where to locate it. How can I fix this? Please help. Im running Yosemite. I have XCode installed and the XCode Tools. I have been running MacPorts successfully for years on this station. Ever since the selfupdate today it broke. I cannot upgrade to High Sierra because we use an XSan system over fibre and the newer versions of OS X don't support our setup. I even tried uninstalling all my ports and deleting macports all together and then re-installing from scratch. Still gives me that error about the config file.

[raimue (Rainer Müller)]

Can you attach a main.log showing the error? On which version of macOS are you? Does /usr/include exist on your system?

[raimue (Rainer Müller)]

Ah, sorry, I did not see it at first: Mac OS X 10.10 Yosemite.

[jmroot (Joshua Root)]

What result do you get from running xcrun --sdk macosx10.10 --show-sdk-path?