ICU relying on undef is not viable in cross-compile scenario

config_host.mk.in

@@ -155,9 +155,9 @@ export HUNSPELL_CFLAGS="@HUNSPELL_CFLAGS@"
 export HUNSPELL_LIBS="@HUNSPELL_LIBS@"
 export HYPHEN_LIB="@HYPHEN_LIB@"
 export HYPH_SYSTEM_DIR="@HYPH_SYSTEM_DIR@"
-@x_ICU@ export ICU_MAJOR="@ICU_MAJOR@"
-@x_ICU@ export ICU_MICRO="@ICU_MICRO@"
-@x_ICU@ export ICU_MINOR="@ICU_MINOR@"
+export ICU_MAJOR="@ICU_MAJOR@"
+export ICU_MICRO="@ICU_MICRO@"
+export ICU_MINOR="@ICU_MINOR@"
 export ICU_RECLASSIFIED_CLOSE_PARENTHESIS="@ICU_RECLASSIFIED_CLOSE_PARENTHESIS@"
 export INPATH="@INPATH@"
 export INPATH_FOR_BUILD="@INPATH_FOR_BUILD@"

configure.in

@@ -6598,8 +6598,7 @@ dnl ===================================================================
 SYSTEM_GENBRK=
 SYSTEM_GENCCODE=
 SYSTEM_GENCMN=
-# x_ICU us used to comment-out ICU_MAJOR/MINOR/MICRO in config_host.mk
-x_ICU=
+
 ICU_MAJOR=
 ICU_MINOR=
 ICU_MICRO=
@@ -6654,13 +6653,11 @@ if test "$with_system_icu" = "yes"; then
     MINGW_EXTERNAL_DLLS="$MINGW_EXTERNAL_DLLS icui18n$ICU_MAJOR$ICU_MINOR.dll icuuc$ICU_MAJOR$ICU_MINOR.dll icudata$ICU_MAJOR$ICU_MINOR.dll"
 else
     AC_MSG_RESULT([internal])
-    x_ICU=[\#]
     SYSTEM_ICU="NO"
     ICU_RECLASSIFIED_CLOSE_PARENTHESIS="YES"
     BUILD_TYPE="$BUILD_TYPE ICU"
 fi
 
-AC_SUBST(x_ICU)
 AC_SUBST(SYSTEM_ICU)
 AC_SUBST(SYSTEM_GENBRK)
 AC_SUBST(SYSTEM_GENCCODE)

icu/icuversion.mk

@@ -24,10 +24,15 @@
 # for a copy of the LGPLv3 License.
 #
 #*************************************************************************
-# major 
-ICU_MAJOR*=4
-# minor 
-ICU_MINOR*=4
-# micro 
-ICU_MICRO*=2
-
+# major
+.IF "$(ICU_MAJOR)" = ""
+ICU_MAJOR=4
+.ENDIF
+# minor
+.IF "$(ICU_MINOR)" = ""
+ICU_MINOR=4
+.ENDIF
+# micro
+.IF "$(ICU_MICRO)" = ""
+ICU_MICRO=2
+.ENDIF