pin older cython and add patch to disable pthread in pypocketfft

recipes/recipes_emscripten/scipy/patches/0016-disable-pthread-pypocketfft.patch

@@ -0,0 +1,17 @@
+diff --git a/scipy/fft/_pocketfft/setup.py b/scipy/fft/_pocketfft/setup.py
+index 7e4456501..f5c682986 100644
+--- a/scipy/fft/_pocketfft/setup.py
++++ b/scipy/fft/_pocketfft/setup.py
+@@ -11,9 +11,9 @@ def pre_build_hook(build_ext, ext):
+         args.append('/EHsc')
+     else:
+         # Use pthreads if available
+-        has_pthreads = try_compile(cc, code='#include <pthread.h>\n'
+-                                   'int main(int argc, char **argv) {}')
+-        if has_pthreads:
++        # has_pthreads = try_compile(cc, code='#include <pthread.h>\n'
++        #                            'int main(int argc, char **argv) {}')
++        if False:
+             ext.define_macros.append(('POCKETFFT_PTHREADS', None))
+             if has_flag(cc, '-pthread'):
+                 args.append('-pthread')

recipes/recipes_emscripten/scipy/recipe.yaml

@@ -31,6 +31,7 @@ source:
       - patches/0013-Add-extra-END-to-prini.f.patch
       - patches/0014-BUG-Fix-signature-of-D_IIR_forback-1-2.patch
       - patches/0015-disable-longdouble.patch
+      - patches/0016-disable-pthread-pypocketfft.patch
 
   # https://github.com/scipy/scipy/tree/v{{ version }}/scipy/_lib
   - git_url: https://github.com/scipy/boost-headers-only.git
@@ -51,7 +52,7 @@ requirements:
   build:
     - sel(build_platform != target_platform): python
     - sel(build_platform != target_platform): cross-python_{{ target_platform }}
-    - sel(build_platform != target_platform): cython
+    - sel(build_platform != target_platform): cython 0.29.30
     # we need gcc and gfortran for the preprocessor!
     - gcc_impl_linux-64
     - gfortran_impl_linux-64