If I recall correctly, the original compilation target is not even /bin/bash but the /bin/sh. Originally, the ./configure script generated by autoconf must run

If I recall correctly, the original compilation target is not even /bin/bash but the /bin/sh. Originally, the ./configure script generated by autoconf must run on several incompatible flavors of Unix at that time, including AIX, SunOS, and BSD, powered by several different CPU architectures, such as x86, Alpha, SPARC, and MIPS, so shipping binaries or using the Bash syntax was not acceptable. It must strictly use the original sh syntax. Though I suspect lots of Bashism has lurked in over the years since nobody still tests it anymore.