[autoconf] Add autoconf v2.71 (#6582)

A/autoconf/build_tarballs.jl

@@ -0,0 +1,27 @@
+using BinaryBuilder
+
+name = "autoconf"
+version = v"2.71"
+
+# Collection of sources required to complete build
+sources = [
+    ArchiveSource("https://ftp.gnu.org/gnu/autoconf/autoconf-$(version.major).$(version.minor).tar.xz",
+                  "f14c83cfebcc9427f2c3cea7258bd90df972d92eb26752da4ddad81c87a0faa4")
+]
+
+# Bash recipe for building across all platforms
+script = raw"""
+cd $WORKSPACE/srcdir/autoconf*/
+./configure --prefix=${prefix} --build=${MACHTYPE} --host=${target}
+make -j${nproc}
+make install
+"""
+
+platforms = supported_platforms()
+products = [
+    FileProduct("bin/autoconf", :autoconf),
+]
+
+dependencies = Dependency[
+]
+build_tarballs(ARGS, name, version, sources, script, platforms, products, dependencies; julia_compat="1.6")