gnu: Python: Fix test failure on ARMv7.

* gnu/packages/patches/python-3-arm-alignment.patch: New file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/python.scm (python-3.8)[source](patches): Add it when the
current system is ARM.

gnu/packages/patches/python-3-arm-alignment.patch

@@ -0,0 +1,21 @@
+Ensure memory accesses in the sha3 module are aligned on ARM as it causes
+problems when running 32-bit code on a 64-bit kernel.
+
+Patch taken from upstream bug report:
+https://bugs.python.org/issue36515
+
+--- a/Modules/_sha3/sha3module.c
++++ b/Modules/_sha3/sha3module.c
+@@ -64,6 +64,12 @@
+ #define PLATFORM_BYTE_ORDER IS_BIG_ENDIAN
+ #endif
+ 
++/* Bus error on 32-bit ARM due to un-aligned memory accesses; 64-bit ARM
++ * doesn't complain but un-aligned memory accesses are sub-optimal */
++#if defined(__arm__) || defined(__aarch64__)
++#define NO_MISALIGNED_ACCESSES
++#endif
++
+ /* mangle names */
+ #define KeccakF1600_FastLoop_Absorb _PySHA3_KeccakF1600_FastLoop_Absorb
+ #define Keccak_HashFinal _PySHA3_Keccak_HashFinal