fix(install.sh): skip checking for sse4 2 flag if kvm was detected (#485)

This PR disables checking for the SSE4.2 flag, which may not be present if the server is running in a VM even if SSE4.2 is in fact available to use (ClickHouse/ClickHouse#20). The KVM check was obtained from a [comment](https://github.com/ClickHouse/ClickHouse/issues/20#issuecomment-226849297) in that issue.

If SSE4.2 is not actually available in the VM, then the installation script may fail in an unpredictable way. Perhaps we can add a keyword argument to the script to let the user decide if they want to skip the check.

install.sh

@@ -65,11 +65,15 @@ if [ "$RAM_AVAILABLE_IN_DOCKER" -lt "$MIN_RAM" ]; then
 fi
 
 #SSE4.2 required by Clickhouse (https://clickhouse.yandex/docs/en/operations/requirements/)
-SUPPORTS_SSE42=$(docker run --rm busybox grep -c sse4_2 /proc/cpuinfo || :);
+# On KVM, cpuinfo could falsely not report SSE 4.2 support, so skip the check. https://github.com/ClickHouse/ClickHouse/issues/20#issuecomment-226849297
+IS_KVM=$(docker run --rm busybox grep -c 'Common KVM processor' /proc/cpuinfo || :)
+if (($IS_KVM == 0)); then
+  SUPPORTS_SSE42=$(docker run --rm busybox grep -c sse4_2 /proc/cpuinfo || :)
   if (($SUPPORTS_SSE42 == 0)); then
     echo "FAIL: The CPU your machine is running on does not support the SSE 4.2 instruction set, which is required for one of the services Sentry uses (Clickhouse). See https://git.io/JvLDt for more info."
     exit 1
   fi
+fi
 
 # Clean up old stuff and ensure nothing is working while we install/update
 # This is for older versions of on-premise: