tergent: reformat build.sh and remove redundant stuff

packages/tergent/build.sh

@@ -2,18 +2,7 @@ TERMUX_PKG_HOMEPAGE=https://github.com/aeolwyr/tergent
 TERMUX_PKG_DESCRIPTION="An ssh-agent implementation for Termux that uses Android Keystore as its backend"
 TERMUX_PKG_LICENSE="Apache-2.0"
 TERMUX_PKG_VERSION=0.1.1
-TERMUX_PKG_SHA256=b16e5ba1a9333d6e14b94d8cf3f5ad27d3af124f6f2bbebb0eca62ac95783281
 TERMUX_PKG_SRCURL=https://github.com/aeolwyr/tergent/archive/${TERMUX_PKG_VERSION}.tar.gz
+TERMUX_PKG_SHA256=b16e5ba1a9333d6e14b94d8cf3f5ad27d3af124f6f2bbebb0eca62ac95783281
 TERMUX_PKG_DEPENDS="termux-api"
-
-termux_step_pre_configure() {
-	termux_setup_rust
-}
-
-termux_step_make_install() {
-	cd $TERMUX_PKG_SRCDIR
-
-	cargo build --target=$CARGO_TARGET_NAME --release
-
-	cp target/$CARGO_TARGET_NAME/release/tergent $TERMUX_PREFIX/bin/tergent
-}
+TERMUX_PKG_BUILD_IN_SRC=true