docs/devel: fix bash-ism warning for configure

Hopefully this makes the meaning clearer.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260114101525.4039244-1-alex.bennee@linaro.org
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>

docs/devel/build-system.rst

@@ -66,7 +66,7 @@ Modifying ``configure``
 ``configure`` is a shell script; it uses ``#!/bin/sh`` and therefore
 should be compatible with any POSIX shell. It is important to avoid
 using bash-isms to avoid breaking development platforms where bash is
-the primary host.
+not the default shell implementation.
 
 The configure script provides a variety of functions to help writing
 portable shell code and providing consistent behavior across architectures