From config.log:
configure:7443: checking for pkg-config
configure:7466: found /mnt/c/Strawberry/perl/bin/pkg-config
configure:7478: result: /mnt/c/Strawberry/perl/bin/pkg-config
It's picking up pkg-config from your Windows install. Remote /mnt/c/Strawberry/perl/bin/ from your PATH, and/or install the packages that the Sage top-level configure script recommends to install.