configure: Remove unused "require config" option

configure

@@ -85,8 +85,6 @@ Configure $APP_NAME prior to building.
                             usable for eg distcc or ccache.
 --linker=CC                 The linker to use when building modules.
                             Default is $LD
---require-config            Will cause $APP_NAME to refuse to run when
-                            it fails to find a configuration file
 --no-example-certs          Disables generation of example certificates.
 EOF
 }
@@ -248,9 +246,6 @@ do
       DATADIR="$value"
       DATADIR_SET=yes
       ;;
-   --require-config)
-      REQUIRE_CONFIG=yes
-      ;;
    --lua-suffix)
       [ -n "$value" ] || die "Missing value in flag $key."
       LUA_SUFFIX="$value"
@@ -585,7 +580,6 @@ LUA_INCDIR=$LUA_INCDIR
 LUA_LIBDIR=$LUA_LIBDIR
 LUA_BINDIR=$LUA_BINDIR
 MULTIARCH_SUBDIR=$MULTIARCH_SUBDIR
-REQUIRE_CONFIG=$REQUIRE_CONFIG
 IDN_LIB=$IDN_LIB
 IDNA_LIBS=$IDNA_LIBS
 OPENSSL_LIBS=$OPENSSL_LIBS