Add make archive to create a Carthage prebuild binary

.gitignore

@@ -16,6 +16,8 @@ DerivedData/
 *.perspectivev3
 !default.perspectivev3
 xcuserdata/
+RxCombine.xcodeproj
+Package.resolved
 
 ## Other
 *.moved-aside

Makefile

@@ -0,0 +1,2 @@
+archive:
+	scripts/carthage-archive.sh

scripts/carthage-archive.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+
+if ! which carthage > /dev/null; then
+    echo 'Error: Carthage is not installed' >&2
+    exit 1
+fi
+
+if [ ! -f Package.swift ]; then
+    echo "Package.swift can't be found, please make sure you run scripts/carthage-archive.sh from the root folder" >&2
+    exit 1
+fi
+
+if ! which swift > /dev/null; then
+    echo 'Swift is not installed' >&2
+    exit 1
+fi
+
+REQUIRED_SWIFT_TOOLING="5.1.0"
+TOOLS_VERSION=`swift package tools-version`
+
+if [ ! "$(printf '%s\n' "$REQUIRED_SWIFT_TOOLING" "$TOOLS_VERSION" | sort -V | head -n1)" = "$REQUIRED_SWIFT_TOOLING" ]; then
+    echo 'You must have Swift Package Manager 5.1.0 or later.'
+    exit 1
+fi
+
+swift package generate-xcodeproj
+carthage build --no-skip-current
+carthage archive
+
+echo "Upload RxCombine.framework.zip to the latest release"