Configurable iconv header and library locations

Should help to fix the build on OpenBSD (together with a corresponding
patch to libraries/base).

configure.ac

@@ -193,6 +193,25 @@ AC_SUBST([WithGhc])
 dnl ** Without optimization some INLINE trickery fails for GHCi
 SRC_CC_OPTS="-O"
 
+dnl Allow to specify iconv options to the toplevel configure script
+dnl so they can be properly passed to sub-builds.
+dnl Note: ICONV_LIB_DIRS and ICONV_INCLUDE_DIRS are not predefined
+dnl to the empty string to allow them to be overridden from the
+dnl environment.
+
+AC_ARG_WITH([iconv-includes],
+  [AC_HELP_STRING([--with-iconv-includes],
+    [directory containing iconv.h])],
+    [ICONV_INCLUDE_DIRS=$withval])
+
+AC_ARG_WITH([iconv-libraries],
+  [AC_HELP_STRING([--with-iconv-libraries],
+    [directory containing iconv library])],
+    [ICONV_LIB_DIRS=$withval])
+
+AC_SUBST(ICONV_INCLUDE_DIRS)
+AC_SUBST(ICONV_LIB_DIRS)
+
 dnl--------------------------------------------------------------------
 dnl * Choose host(/target/build) platform
 dnl--------------------------------------------------------------------

mk/config.mk.in

@@ -944,6 +944,15 @@ WAY_o_HC_OPTS=
 
 CONFIGURE_ARGS = @CONFIGURE_ARGS@
 
+################################################################################
+#
+#    To be passed to sub-builds
+#
+################################################################################
+
+ICONV_INCLUDE_DIRS = @ICONV_INCLUDE_DIRS@
+ICONV_LIB_DIRS = @ICONV_LIB_DIRS@
+
 ################################################################################
 #
 #    Bindist testing directory

rules/build-package-data.mk

@@ -30,6 +30,14 @@ endif
 $1_$2_CONFIGURE_OPTS += --configure-option=CFLAGS="$$(filter-out -Werror,$$(SRC_CC_OPTS)) $$($1_CC_OPTS) $$($1_$2_CC_OPTS)"
 $1_$2_CONFIGURE_OPTS += --configure-option=LDFLAGS="$$(SRC_LD_OPTS) $$($1_LD_OPTS) $$($1_$2_LD_OPTS)"
 
+ifneq "$$(ICONV_INCLUDE_DIRS)" ""
+$1_$2_CONFIGURE_OPTS += --configure-option=--with-iconv-includes="$$(ICONV_INCLUDE_DIRS)"
+endif
+
+ifneq "$$(ICONV_LIB_DIRS)" ""
+$1_$2_CONFIGURE_OPTS += --configure-option=--with-iconv-libraries="$$(ICONV_LIB_DIRS)"
+endif
+
 # This rule configures the package, generates the package-data.mk file
 # for our build system, and registers the package for use in-place in
 # the build tree.