all.sh: disable MEMORY_BUFFER_ALLOC in cmake asan build

Enabling MBEDTLS_MEMORY_BUFFER_ALLOC_C bypasses ASan leak checks
because system calloc() and free() aren't used. 
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 244fdc3..20458af 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -701,7 +701,7 @@
     # full minus MBEDTLS_USE_PSA_CRYPTO: run the same set of tests as basic-build-test.sh
     msg "build: cmake, full config + MBEDTLS_USE_PSA_CRYPTO, ASan"
     scripts/config.pl full
-    scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # too slow for tests
+    scripts/config.pl unset MBEDTLS_MEMORY_BUFFER_ALLOC_C
     scripts/config.pl set MBEDTLS_ECP_RESTARTABLE  # not using PSA, so enable restartable ECC
     scripts/config.pl set MBEDTLS_PSA_CRYPTO_C
     scripts/config.pl unset MBEDTLS_USE_PSA_CRYPTO