boost: fix build error

Thanks to pullmoll.

Fixes: #11228

srcpkgs/boost/template

@@ -1,7 +1,7 @@
 # Template file for 'boost'
 pkgname=boost
 version=1.69.0
-revision=2
+revision=3
 wrksrc="${pkgname}_${version//\./_}"
 hostmakedepends="bzip2-devel icu-devel python-devel python3-devel"
 makedepends="zlib-devel bzip2-devel icu-devel python-devel python3-devel"
@@ -122,7 +122,7 @@ boost-build_package() {
 	short_desc+=" - Boost.Build framework"
 	pkg_install() {
 		vmove usr/share/boost-build
-		vmove etc
+		vmove etc/site-config.jam
 	}
 }
 boost-devel_package() {