Add support for `RUBY_CONFIGURE_OPTS` and `RUBY_MAKE_OPTS`

These variables let you pass Ruby-specific configure and make options
that will not be passed to dependent packages like libyaml.

README.md

@@ -137,6 +137,9 @@ process.
   specifying GNU make (`gmake`) on some systems.
 * `MAKE_OPTS` (or `MAKEOPTS`) lets you pass additional options to
   `make`.
+* `RUBY_CONFIGURE_OPTS` and `RUBY_MAKE_OPTS` allow you to specify
+  configure and make options for buildling MRI. These variables will
+  be passed to Ruby only, not any dependent packages (e.g. libyaml).
 
 ### Checksum verification
 

bin/ruby-build

@@ -305,7 +305,7 @@ build_package() {
   echo "Installing ${package_name}..." >&2
 
   for command in $commands; do
-    "build_package_${command}"
+    "build_package_${command}" "$package_name"
   done
 }
 
@@ -318,8 +318,13 @@ build_package_standard() {
     MAKE_OPTS="-j 2"
   fi
 
-  { ./configure --prefix="$PREFIX_PATH" $CONFIGURE_OPTS
-    "$MAKE" $MAKE_OPTS
+  # Support YAML_CONFIGURE_OPTS, RUBY_CONFIGURE_OPTS, etc.
+  local package_var_name="$(echo "${package_name%%-*}" | tr a-z A-Z)"
+  local PACKAGE_CONFIGURE_OPTS="${package_var_name}_CONFIGURE_OPTS"
+  local PACKAGE_MAKE_OPTS="${package_var_name}_MAKE_OPTS"
+
+  { ./configure --prefix="$PREFIX_PATH" $CONFIGURE_OPTS ${!PACKAGE_CONFIGURE_OPTS}
+    "$MAKE" $MAKE_OPTS ${!PACKAGE_MAKE_OPTS}
     "$MAKE" install
   } >&4 2>&1
 }