Andreas V. Meier:

package/public/boost/boost.conf

@@ -26,10 +26,12 @@ makeinstopt=
 
 # otherwise rebuilding boost does not reinstall static files
 #var_insert taropt ' ' -m
+icu=0
+pkginstalled libicu && icu=1
 
 hook_add preconf 3 "rm configure"
-hook_add inmake 5 "bjam -sTOOLS=gcc"
+hook_add inmake 5 "bjam -sTOOLS=gcc -sHAVE_ICU=$icu"
 hook_add postmake 5 "bjam --prefix=$prefix --libdir=$libdir \
-                     --includedir=$includedir -sTOOLS=gcc -sHAVE_ICU=0 --layout=system \
+                     --includedir=$includedir -sTOOLS=gcc -sHAVE_ICU=$icu --layout=system \
                      install"