dev-vcs/git-crypt: cleanup install handling

- pass DESTDIR rather than overload PREFIX. Supported since 2014:
  73bf395b3b

  While we are at it, handle Prefix. It is totally trivial.

- remove very outdated dodir entirely. Since 2015, the Makefile creates
  directories as needed!
  ede1461563

Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>

dev-vcs/git-crypt/git-crypt-0.7.0.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2022 Gentoo Authors
+# Copyright 1999-2025 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=8
@@ -30,6 +30,5 @@ src_configure() {
 }
 
 src_install() {
-	dodir /usr/bin
-	emake PREFIX="${D}"/usr install
+	emake DESTDIR="${D}" PREFIX="${EPREFIX}/usr" install
 }