Fix python312 + icu cross-compilation blockers

python312: Added --disable-test-modules to host build configure flags.
The host build (needed as dev-dependency for cross-compile) was
trying to compile test modules (_testmultiphase, xxlimited, etc.)
which fail on this system. The cross-compile already had this flag.

icu: Added --disable-tools to cross-compile configure flags. The ICU
data tools (genrb, derb) try to link against cross-compiled static
libraries, causing C++ vtable linker errors (undefined reference
to vtable for UTF16CollationIterator). Tools are built in the host
step; cross-compile only needs the libraries.

Combined with zsh --srcdir, base staging mkdir, and netstack fix,
these unblock the redbear-mini build.

recipes/dev/python312/recipe.toml

@@ -48,7 +48,7 @@ if [ "$TARGET" != "$COOKBOOK_HOST_TARGET" ]; then
         ac_cv_exeext=""
     )
 else
-    COOKBOOK_CONFIGURE_FLAGS=(--prefix=/usr)
+    COOKBOOK_CONFIGURE_FLAGS=(--prefix=/usr --disable-test-modules)
 fi
 
 if [ "${COOKBOOK_DYNAMIC}" != "1" ]; then