testing/libmpfi: rename from mpfi

Also add a static subpackage

testing/libmpfi/APKBUILD

@@ -1,6 +1,6 @@
 # Contributor: Grigory Kirillov <txgk@bk.ru>
 # Maintainer: Grigory Kirillov <txgk@bk.ru>
-pkgname=mpfi
+pkgname=libmpfi
 pkgver=1.5.4
 pkgrel=0
 pkgdesc="Library for multiple precision interval arithmetic"
@@ -15,8 +15,9 @@ makedepends="
 	mpfr-dev
 	"
 options="!check" # tests are broken
-subpackages="$pkgname-dev $pkgname-doc"
+subpackages="$pkgname-static $pkgname-dev $pkgname-doc"
 source="https://github.com/arpra-project/mpfi/archive/$pkgver/mpfi-$pkgver.tar.gz"
+builddir="$srcdir/mpfi-$pkgver"
 
 prepare() {
 	default_prepare
@@ -30,8 +31,7 @@ build() {
 		--target="$CTARGET" \
 		--build="$CBUILD" \
 		--host="$CHOST" \
-		--prefix=/usr \
-		--disable-static
+		--prefix=/usr
 	make
 }