cleanup: remove reference to $1_$2_CONFIGURE_FLAGS, which is never used

we also have $1_$2_CONFIGURE_OPTS, which is used.

rules/build-package-data.mk

@@ -24,7 +24,7 @@ endif
 # for our build system, and registers the package for use in-place in
 # the build tree.
 $1/$2/package-data.mk $1/$2/inplace-pkg-config $1/$2/build/autogen/cabal_macros.h : $$(GHC_CABAL_INPLACE) $$($1_$2_GHC_PKG_DEP) $1/$$($1_PACKAGE).cabal $$(wildcard $1/configure) $$($1_$2_HC_CONFIG_DEP)
-	$$(GHC_CABAL_INPLACE) configure --with-ghc=$$($1_$2_HC_CONFIG) --with-ghc-pkg=$$($1_$2_GHC_PKG) --with-gcc=$$(WhatGccIsCalled) --configure-option=--with-cc=$$(WhatGccIsCalled) $$($1_$2_CONFIGURE_FLAGS) $$($1_CONFIGURE_OPTS) $$($1_$2_CONFIGURE_OPTS) -- $2 $1
+	$$(GHC_CABAL_INPLACE) configure --with-ghc=$$($1_$2_HC_CONFIG) --with-ghc-pkg=$$($1_$2_GHC_PKG) --with-gcc=$$(WhatGccIsCalled) --configure-option=--with-cc=$$(WhatGccIsCalled) $$($1_CONFIGURE_OPTS) $$($1_$2_CONFIGURE_OPTS) -- $2 $1
 	if [ "$$($1_$2_PROG)" = "" ]; then \
 	    $$($1_$2_GHC_PKG) update --force $$($1_$2_GHC_PKG_OPTS) $1/$2/inplace-pkg-config; \
 	fi