diff --git a/LLVM.makefile b/LLVM.makefile
index cef5095a..d002a44a 100644
--- a/LLVM.makefile
+++ b/LLVM.makefile
@@ -74,6 +74,7 @@ $(BUILD_DIR)/llvm.BUILT:
 		install-llvm-ranlib \
 		install-llvm-strip \
 		install-llvm-dwarfdump \
+		install-llvm-symbolizer \
 		install-clang-resource-headers \
 		install-ar \
 		install-ranlib \
diff --git a/faasmtools/build.py b/faasmtools/build.py
index ffa45d39..37db8a11 100644
--- a/faasmtools/build.py
+++ b/faasmtools/build.py
@@ -73,6 +73,7 @@
 WASM_CFLAGS = [
     "-O3",
     # "-mno-atomics",
+    # TODO: may want to use -mrelaxed-simd instead
     "-msimd128",
     "--sysroot={}".format(WASM_SYSROOT),
     "-m32",
@@ -329,21 +330,46 @@ def get_dict_as_cmake_vars(env_dict):
 ]
 
 
-def build_config_cmd(cmd, shared=False, cxx=False, conf_args=True):
+def build_config_cmd(env_vars, cmd, shared=False, cxx=False, conf_args=True):
     """
     Wraps an autotools command in the relevant environment variables and
-    cross-compilation config
+    cross-compilation config. We need to call this method after we get
+    the right env. vars using get_faasm_build_env_dict
     """
-    result = copy(BASE_CONFIG_CMDXX if cxx else BASE_CONFIG_CMD)
+    base_config_cmd = [
+        "CC={}".format(env_vars["FAASM_WASM_CC"]),
+        "CXX={}".format(env_vars["FAASM_WASM_CXX"]),
+        # "CPP={}".format(env_vars["FAASM_WASM_CXX"]),
+        "AR={}".format(env_vars["FAASM_WASM_AR"]),
+        "RANLIB={}".format(env_vars["FAASM_WASM_RANLIB"]),
+        'CFLAGS="--target={} {}"'.format(env_vars["FAASM_WASM_TRIPLE"], env_vars["FAASM_WASM_CFLAGS"]),
+        # 'CPPFLAGS="--target={} {}"'.format(env_vars["FAASM_WASM_TRIPLE"], env_vars["FAASM_WASM_CXXFLAGS"]),
+        'CXXFLAGS="--target={} {}"'.format(env_vars["FAASM_WASM_TRIPLE"], env_vars["FAASM_WASM_CXXFLAGS"]),
+        'CCSHARED="{}"'.format(env_vars["FAASM_WASM_CFLAGS_SHARED"]),
+        'CXXSHARED="{}"'.format(env_vars["FAASM_WASM_CXXFLAGS_SHARED"]),
+    ]
+
+    if cxx:
+        base_config_cmd += [
+            "LD={}".format(env_vars["FAASM_WASM_CXX"]),
+            'LDFLAGS="-target {} {}"'.format(env_vars["FAASM_WASM_TRIPLE"], env_vars["FAASM_WASM_STATIC_LINKER_FLAGS"])
+            # 'LDSHARED="{}"'.format(WASM_LDXXSHARED),
+        ]
+    else:
+        base_config_cmd += [
+            "LD={}".format(env_vars["FAASM_WASM_CC"]),
+            'LDFLAGS="-target {} {}"'.format(env_vars["FAASM_WASM_TRIPLE"], env_vars["FAASM_WASM_STATIC_LINKER_FLAGS"])
+            # 'LDSHARED="{}"'.format(env_vars["FAASM_WASM_CFLAGS_SHARED"),
+        ]
 
-    result += BASE_CONFIG_FLAGS_SHARED if shared else BASE_CONFIG_FLAGS
+    # result += BASE_CONFIG_FLAGS_SHARED if shared else BASE_CONFIG_FLAGS
 
-    result += cmd
+    base_config_cmd += cmd
 
     if conf_args:
-        result += _BASE_CONFIG_ARGS_SHARED if shared else _BASE_CONFIG_ARGS
+        base_config_cmd += _BASE_CONFIG_ARGS_SHARED if shared else _BASE_CONFIG_ARGS
 
-    return result
+    return base_config_cmd
 
 
 def run_autotools(proj_dir):
diff --git a/sysroot_extras/libc.imports b/sysroot_extras/libc.imports
index 581cc36b..d0ef7134 100644
--- a/sysroot_extras/libc.imports
+++ b/sysroot_extras/libc.imports
@@ -99,11 +99,16 @@ pthread_cond_destroy
 pthread_cond_signal
 pthread_cond_timedwait
 pthread_cond_init
+pthread_condattr_init
+pthread_condattr_setclock
 pthread_equal
 pthread_mutexattr_init
 pthread_mutexattr_settype
 pthread_mutexattr_destroy
+__tls_align
 __tls_base
+__tls_size
+__wasm_init_tls
 
 # Signals
 signal
diff --git a/tasks/libemscripten.py b/tasks/libemscripten.py
index 2a034942..7a7022a8 100644
--- a/tasks/libemscripten.py
+++ b/tasks/libemscripten.py
@@ -3,8 +3,8 @@
 
 
 @task(default=True)
-def build(ctx, clean=False):
+def build(ctx, clean=False, threads=False):
     """
     Builds Faasm emscripten support library
     """
-    build_faasm_lib("libemscripten", clean=clean, native=False, shared=False)
+    build_faasm_lib("libemscripten", clean=clean, native=False, shared=False, threads=threads)
diff --git a/third-party/wasi-libc b/third-party/wasi-libc
index b37edadc..dceadb68 160000
--- a/third-party/wasi-libc
+++ b/third-party/wasi-libc
@@ -1 +1 @@
-Subproject commit b37edadc81a9c24b3c4c93f1ba8e14210144832f
+Subproject commit dceadb68111821fc2ba9ba3a64b95463b21cd9db