Ensure fontconfig includes platform-relevant config location (#57)

Co-authored-by: Kleis Auke Wolthuizen <github@kleisauke.nl>

Author: lovell

build/lin.sh

@@ -281,7 +281,8 @@ mkdir ${DEPS}/fontconfig
 curl -Ls https://www.freedesktop.org/software/fontconfig/release/fontconfig-${VERSION_FONTCONFIG}.tar.xz | tar xJC ${DEPS}/fontconfig --strip-components=1
 cd ${DEPS}/fontconfig
 ./configure --host=${CHOST} --prefix=${TARGET} --enable-static --disable-shared --disable-dependency-tracking \
-  --with-expat-includes=${TARGET}/include --with-expat-lib=${TARGET}/lib --sysconfdir=${TARGET}/etc --disable-docs
+  --with-expat-includes=${TARGET}/include --with-expat-lib=${TARGET}/lib ${LINUX:+--sysconfdir=/etc} \
+  ${DARWIN:+--sysconfdir=/usr/local/etc} --disable-docs
 make install-strip
 
 mkdir ${DEPS}/harfbuzz