Looks like a corrupted toolchain to me. Please follow Unable to resolve configuration with compiler path ERROR and generating random files in projects - #10 by slopsjon to make sure you have the release version of the C/C++ extension by microsoft so that it does not corrupt your files. Then, delete every folder in <home folder>/.platformio/packages, <home folder>/.platformio/.cache and <home folder>/.platformio/platforms and rebuild the project. It will take a while for PlatformIO to redownload its packages.