test: bump the base VM memory to 768M

as with 512M some tests occasionally trip off OOM-killer (e.g.
TEST-64 + multipath).

test/TEST-36-NUMAPOLICY/test.sh

@@ -9,7 +9,7 @@ TEST_NO_NSPAWN=1
 . "${TEST_BASE_DIR:?}/test-functions"
 
 if qemu_min_version "5.2.0"; then
-    QEMU_OPTIONS="-object memory-backend-ram,id=mem0,size=${QEMU_MEM:-512M} -numa node,memdev=mem0,nodeid=0"
+    QEMU_OPTIONS="-object memory-backend-ram,id=mem0,size=${QEMU_MEM:-768M} -numa node,memdev=mem0,nodeid=0"
 else
     QEMU_OPTIONS="-numa node,nodeid=0"
 fi

test/test-functions

@@ -483,7 +483,7 @@ run_qemu() {
     qemu_options+=(
         -smp "$QEMU_SMP"
         -net none
-        -m "${QEMU_MEM:-512M}"
+        -m "${QEMU_MEM:-768M}"
         -nographic
         -kernel "$KERNEL_BIN"
         -drive "format=raw,cache=unsafe,file=$image"