Write Autotools configuration

Add Autotools configuration files for building binaries.

configure.ac

@@ -0,0 +1,63 @@
+# Title, version, etc.
+AC_INIT(\
+        [RTR], \
+        [0.1.0], \
+        [mail@acm.contact], \
+        [rtr], \
+        [https://www.delay.cloud/] \
+        )
+
+# AC_CHECK_LIB is not utilized, since it checks the presence of libraries by
+# linking them to test program; this process introduces more overhead and longer
+# build times.
+
+# Define BUILD in order to enable inclusion of config.h, which will act as the
+# Autoheader.
+AC_DEFINE([BUILD], [1], [Build system enabled.])
+AM_CONFIG_HEADER([src/config.h])
+
+AC_CONFIG_MACRO_DIR([m4
+                    ])
+
+# Do not generate GNU project files and disable some checks.
+# Includes flags to strictly compile Standard C89.
+AM_INIT_AUTOMAKE([\
+                  foreign \
+                  -Wall \
+                  -Werror \
+                  -Wno-portability \
+                  subdir-objects \
+                  ])
+
+# Option to enable extras.
+AC_ARG_ENABLE([extra],
+    AS_HELP_STRING([--enable-extra], [Enable features]))
+AS_IF([test "x$enable_extra" = "xyes"], [
+  AC_DEFINE([EXTRA], [1], [Enable extra features.])
+  AM_CONDITIONAL([EXTRA], [test "x$enable_extra" = "xyes"])
+])
+
+# Locations of generated Makefiles.
+AC_CONFIG_FILES([\
+                 Makefile \
+                 src/Makefile \
+                 ])
+
+# Primary SDT.
+AC_CONFIG_SRCDIR([src/main.c])
+
+
+CFLAGS="$CFLAGS -std=c89 -pedantic-errors -Wall -Wold-style-definition -Wextra \
+        -Wmissing-prototypes -Wstrict-prototypes" # Compile to C89
+                                                  # without
+                                                  # GNU extensions.
+                                                  # Warnings on.
+
+LT_INIT([shared disable-static]) # Start GNU Libtool. Satic libraries
+                                 # disabled; shared/dynamic linking.
+
+AC_PROG_CC([gcc]) # Autoconf for C compiler; obviously set to use GCC.
+
+AC_OUTPUT # Generate files.
+
+# Possibly add echo here.