Build fails if build directory name includes a comma

Host environment

• Operating system: any
• OS/kernel version: any
• Architecture: any
• QEMU flavor: any
• QEMU version: git master

Description of problem

Builds fail if the build directory name contains a comma.

Steps to reproduce

1. mkdir build,demo && cd build,demo
2. ../configure && make

The linker fails because it uses a wrong build path (comma and trailing part of directory name is missing):

ld: can't read -exported_symbols_list file: /Users/stefan/src/gitlab/qemu-project/qemu/build
clang: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.