Switched build system to meson.

meson.build

@@ -0,0 +1,29 @@
+project('libexim-encrypt-dlfunc', 'c',
+				  default_options: ['b_lundef=false', 'b_pie=true'])
+
+compiler = meson.get_compiler('c')
+conf_data = configuration_data()
+
+sodium_deps = dependency('libsodium')
+
+exim4_code = '''
+#include <stdio.h>
+#include <exim4/local_scan.h>
+int main() {
+    printf("%d\n", LOCAL_SCAN_ABI_VERSION_MAJOR);
+    return 0;
+}
+'''
+
+result = compiler.run(exim4_code)
+local_scan_version = result.stdout().strip().to_int()
+
+if local_scan_version < 3
+   conf_data.set('local_scan_version', 3)
+elif local_scan_version >= 3
+     conf_data.set('local_scan_version', 3)
+else
+	error('exim local_scan version could not be determined')
+endif
+
+subdir('src')