Emit Sort.Order separator before non-first orders in AOT generation

[atirna]

Derived query methods with two or more static OrderBy properties produce Java from the AOT generator that does not compile, so compileAotJava fails and the app cannot build in AOT / GraalVM native mode.

Why

JdbcCodeBlocks.buildSort appended the , separator after each non-first order instead of before, so findAllByOrderByFirstNameAscLastNameDesc() generated:

Sort.by(Sort.Order.asc("firstName")Sort.Order.asc("lastName"), )

which javac rejects with ')' or ',' expected. With one static OrderBy property the loop happened to work because the trailing separator landed after the last (only) order, masking the bug. The separator now goes before each non-first order:

Sort.by(Sort.Order.asc("firstName"), Sort.Order.asc("lastName"))

Single-order emission is unchanged (findTop5ByOrderByAge and its test cover that).

Verification

• before, on current main: ./mvnw -pl spring-data-jdbc verify -Dit.test=JdbcRepositoryContributorIntegrationTests -Dspring.profiles.active=h2: context load fails with CompilationException: Unable to compile source on the malformed Sort.by(...)
• after: same command, Tests run: 38, Failures: 0, Errors: 0
• the new listWithMultipleStaticOrderByProperties inserts a duplicate firstname so the second order key decides the row order, and asserts both keys' effect on the result

Fixes #2377

[schauder]

Thanks, for the PR. That's fixed.