Revert "run-tests: Skip testing arm64ec in msvcrt builds"

This reverts commit 056dd73.

In the current versions of mingw-w64, it is possible to build
the tests for arm64ec with msvcrt.dll as well.

Author: mstorsjo

run-tests.sh

@@ -213,10 +213,6 @@ for arch in $ARCHS; do
         RUN="$RUN_ARM64EC"
         COPY="$COPY_ARM64EC"
         NATIVE="$NATIVE_ARM64EC"
-        if [ -z "$IS_UCRT" ]; then
-            # arm64ec msvcrt isn't working properly yet
-            continue
-        fi
         ;;
     esac