Fix Windows test failure and speed up docs build

Use ucrtbase instead of dlopen(None) for malloc on Windows, fixing
cffi collection error during doctest-modules. Use COMPACT=1 for the
docs Docker build to skip type specializations.

Author: michelp

.github/workflows/docs.yml

@@ -24,6 +24,7 @@ jobs:
           docker build --target psg \
             --build-arg SUITESPARSE=v$(cat GB_VERSION.txt) \
             --build-arg VERSION=99.0.0.0 \
+            --build-arg COMPACT=1 \
             -t psg-docs .
 
       - name: Generate docs with pdoc

suitesparse_graphblas/api/io/binary.py

@@ -1,3 +1,4 @@
+import sys
 from ctypes.util import find_library
 from pathlib import Path
 
@@ -10,7 +11,10 @@
 stdffi.cdef("""
 void *malloc(size_t size);
 """)
-stdlib = stdffi.dlopen(find_library("c"))
+if sys.platform == "win32":
+    stdlib = stdffi.dlopen("ucrtbase")
+else:
+    stdlib = stdffi.dlopen(find_library("c"))
 
 # When "packing" a matrix the owner of the memory buffer is transfered
 # to SuiteSparse, which then becomes responsible for freeing it.  cffi