on msys2, the generated qemu-version.h seems not valid

[Yonggang Luo]

#define QEMU_PKGVERSION ""
#define QEMU_FULL_VERSION "5.1.50"


        pkgversion=$(git describe --match 'v*' --dirty | echo "")
what's echo "" for in qemu-version.sh
-- 
         此致
礼
罗勇刚
Yours
    sincerely,
Yonggang Luo