diff --git a/README.rst b/README.rst
index c0eb8eb..65bd176 100644
--- a/README.rst
+++ b/README.rst
@@ -2,7 +2,7 @@
  ``z3.wasm``
 =============
 
-This repo contains a build script to compile `Z3 <https://github.com/Z3Prover/z3/>`_ to WebAssembly using `emscripten <https://github.com/kripken/emscripten/>`_.  To make things more reproducible, the entire build happens in a `Vagrant <https://www.vagrantup.com/>` VM (but the build script should be fairly platform-agnostic).
+This repo contains a build script to compile `Z3 <https://github.com/Z3Prover/z3/>`_ to WebAssembly using `emscripten <https://github.com/kripken/emscripten/>`_.  To make things more reproducible, the build script may be run in a `Vagrant <https://www.vagrantup.com/>` VM.
 
 Loading Z3 is fairly slow (~15 seconds on Chrome, though less than 1 second on Firefox), but verification typically is within a factor 2 to 5 of native performance.
 
@@ -17,10 +17,15 @@ Install `Vagrant <https://www.vagrantup.com/>`_, then run this::
    vagrant ssh
    VAGRANT=true /vagrant/z3.sh
 
-A detailed log is written to ``provision.log``, with an outline printed to stdout.  The first build can take up to two hours (emscripten requires a custom build of LLVM, Z3 is large, and all of this is running in a VM).
-
+The first build can take up to two hours (emscripten may require a custom build of LLVM, Z3 is large, and all of this is running in a VM).
 The output is written to ``z3w.js``, ``z3w.wasm``, ``z3smt2w.js``, and ``z3smt2w.wasm``.
 
+On Debian/Ubuntu systems, you may prefer to run natively (the build will be much faster)::
+
+   BASEDIR="$(pwd)/build/" ./z3.sh
+
+Some Vagrant configurations can cause clang to crash; in that case, building on a physical machine is the best workaround.
+
 Using the generated code
 ========================
 
diff --git a/z3.sh b/z3.sh
index 0d975d3..35a4c69 100755
--- a/z3.sh
+++ b/z3.sh
@@ -33,8 +33,15 @@
 # * This script is only know to work on Ubuntu. You can run it locally, but in
 #   that case DO NOT set VAGRANT=true.
 
-: "${BASEDIR:=/vagrant}"
 : "${VAGRANT:=false}"
+
+if [ "$VAGRANT" = true ]; then
+    : "${BASEDIR:=/vagrant}"
+else
+    : "${BASEDIR:=$(pwd)/build}"
+fi
+mkdir -p "$BASEDIR"
+
 export DEBIAN_FRONTEND=noninteractive
 
 export JS_ROOT="$BASEDIR/z3-wasm/"
@@ -200,6 +207,8 @@ EMCC_WASM_OPTIONS=(
 EMCC_Z3_JS_INPUTS=("${Z3_ROOT}/build/z3.bc")
 EMCC_Z3_SMT2_JS_INPUTS=("${BASEDIR}/z3smt2.c" "${Z3_ROOT}/build/libz3.a")
 
+cd "$Z3_ROOT"
+
 say '* Z3: Linking (slow!)'; {
     cp "${Z3_ROOT}/build/z3" "${Z3_ROOT}/build/z3.bc"
     # emcc "${EMCC_Z3_OPTIONS[@]}" "${EMCC_Z3_JS_INPUTS[@]}" -o z3.js
@@ -213,5 +222,5 @@ say '* Z3 smt2 client: Linking (slow!)'; {
 
 say ""
 say '*********************************'
-say '***       Setup complete      ***'
+say '***       Build complete      ***'
 say '*********************************'