K2GO-414 fix(proot-builder): disable rsync IDN in the static build (missing libidn2)

The "Build static binaries (PRoot)" workflow started failing in the compile job:
rsync's configure aborts with "Failed to find idn2_lookup_ul function in idn2
lib." (runs #26 and #27 on main, commit ac69e21). build_static.sh git-pulls the
latest termux-packages each run, and the current rsync enables IDN by default and
requires libidn2, which the static build does not provide.

Add --disable-idn to rsync's TERMUX_PKG_EXTRA_CONFIGURE_ARGS, next to the other
feature disables. IDN (internationalized hostnames) is not used on the K2Go rsync
path (local-IP clone/sync); rsync's own configure error recommends this. Upstream
drift, not an app change; proot/aria2/tar/gzip/xz all built. Re-running the build
must now pass rsync and publish a new binaries-* release.

Author: luisguzman-adfa

tools/proot-builder/build_static.sh

@@ -314,7 +314,11 @@ termux_step_pre_configure() {
     mv $TERMUX_PREFIX/lib/libiconv.so* $TERMUX_PREFIX/lib/hidden_so/ 2>/dev/null || true
 
     LDFLAGS+=" -static -ffunction-sections -fdata-sections -Wl,--gc-sections"
-    TERMUX_PKG_EXTRA_CONFIGURE_ARGS+=" --disable-lz4 --disable-zstd --disable-xxhash --disable-openssl --disable-year2038"
+    # K2GO-414: rsync's configure enables IDN by default and needs libidn2 (idn2_lookup_ul),
+    # which this static build does not provide -> configure aborts. IDN (internationalized
+    # hostnames) is not needed for K2Go's local-IP clone/sync, so disable it (rsync's own
+    # configure error recommends --disable-idn).
+    TERMUX_PKG_EXTRA_CONFIGURE_ARGS+=" --disable-lz4 --disable-zstd --disable-xxhash --disable-openssl --disable-idn --disable-year2038"
 
     export ac_cv_func_lchmod=no
     export ac_cv_func_lutimes=no