sci-physics/fastjet: fix build with dash as /bin/sh

configure.ac is full of bash-specific code, so request /bin/bash as
configure shell explicitly.

Package-Manager: Portage-3.0.18, Repoman-3.0.3
Signed-off-by: Andrew Savchenko <bircoph@gentoo.org>

sci-physics/fastjet/fastjet-3.0.6-r2.ebuild

@@ -33,6 +33,7 @@ src_configure() {
 	use cgal && \
 		has_version 'sci-mathematics/cgal[gmp]' && append-libs -lgmp
 
+	CONFIG_SHELL="${EPREFIX}/bin/bash" \
 	econf \
 		--disable-static \
 		$(use_enable cgal) \