filesystem: fix missing CONFIG_SITE breaking configure host detection

We want configure to always go through our config.site. It first
looks at CONFIG_SITE, then the prefix if there is one and then falls
back to our default. But this means if a prefix is set it wouldn't
use it.

Fix this by setting CONFIG_SITE always like before.

Broken by 9a37bb560a

filesystem/PKGBUILD

@@ -5,7 +5,7 @@
 
 pkgname=filesystem
 pkgver=2021.03
-pkgrel=4
+pkgrel=5
 pkgdesc='Base filesystem'
 arch=('i686' 'x86_64')
 license=('BSD')
@@ -62,7 +62,7 @@ sha256sums=('742a7d66b7a5ebd2b8461728c5b44a46b2305fd2116208eecae5f45828938ea0'
             'ff9edfe41466ef9d2e3adb8dd4f395ebd76bda14448c9a6e9cec5f46c1d81f27'
             '8f4fdf609e18de55e88684d0ee471ac9a8c5dcf126cc63c72d792f9e45789eb1'
             '91f1f918cf13deab0124082086e990786113b0e710dbda4678d8fc14905ad94d'
-            'def19ac4f055ece454857878ddda4d92eb4bf35c518a903247bbc23d745add33'
+            '6446359419e13310d74ab54086271acc2f4ed0dfe97a474cdd06cd7c55ee59a4'
             '6c0ca979c7b146b3750103b1296a399764f4e1b222ee091d3aa072b6da16c1a5'
             'cbec90c9403826bf6d8dd1fed16240b9d8695ec15df5dcdab7e485bb46c016ab'
             '2087410bf7ead6fa586628ea7fc97c53f5ea3ce16d1ee91ecc15ccc18ab53094'

filesystem/profile

@@ -59,6 +59,8 @@ MINGW*|CLANG*|UCRT*)
   PKG_CONFIG_PATH="/usr/lib/pkgconfig:/usr/share/pkgconfig:/lib/pkgconfig"
 esac
 
+CONFIG_SITE="/etc/config.site"
+
 MAYBE_FIRST_START=false
 SYSCONFDIR="${SYSCONFDIR:=/etc}"
 
@@ -146,7 +148,7 @@ then
   export ACLOCAL_PATH
 fi
 
-export PATH MANPATH INFOPATH PKG_CONFIG_PATH USER TMP TEMP PRINTER HOSTNAME PS1 SHELL tmp temp ORIGINAL_TMP ORIGINAL_TEMP ORIGINAL_PATH
+export PATH MANPATH INFOPATH PKG_CONFIG_PATH USER TMP TEMP PRINTER HOSTNAME PS1 SHELL tmp temp ORIGINAL_TMP ORIGINAL_TEMP ORIGINAL_PATH CONFIG_SITE
 unset PATH_SEPARATOR
 
 if [ "$MAYBE_FIRST_START" = "true" ]; then