Update rust to 1.88.0 (#12364)

We keep the practice of keeping the compiler up to date, pointing to the
latest release. This is done by many other projects in the Rust
ecosystem as well.

[Announcement blog
post](https://blog.rust-lang.org/2025/06/26/Rust-1.88.0/)

Prior update was in https://github.com/neondatabase/neon/pull/11938

build-tools.Dockerfile

@@ -179,7 +179,7 @@ RUN curl -sL "https://github.com/peak/s5cmd/releases/download/v${S5CMD_VERSION}/
     && mv s5cmd /usr/local/bin/s5cmd
 
 # LLVM
-ENV LLVM_VERSION=19
+ENV LLVM_VERSION=20
 RUN curl -fsSL 'https://apt.llvm.org/llvm-snapshot.gpg.key' | apt-key add - \
     && echo "deb http://apt.llvm.org/${DEBIAN_VERSION}/ llvm-toolchain-${DEBIAN_VERSION}-${LLVM_VERSION} main" > /etc/apt/sources.list.d/llvm.stable.list \
     && apt update \
@@ -292,7 +292,7 @@ WORKDIR /home/nonroot
 
 # Rust
 # Please keep the version of llvm (installed above) in sync with rust llvm (`rustc --version --verbose | grep LLVM`)
-ENV RUSTC_VERSION=1.87.0
+ENV RUSTC_VERSION=1.88.0
 ENV RUSTUP_HOME="/home/nonroot/.rustup"
 ENV PATH="/home/nonroot/.cargo/bin:${PATH}"
 ARG RUSTFILT_VERSION=0.2.1

pageserver/src/bin/test_helper_slow_client_reads.rs

@@ -37,7 +37,7 @@ async fn main() -> anyhow::Result<()> {
                 not_modified_since: Lsn(23),
             },
             batch_key: 42,
-            message: format!("message {}", msg),
+            message: format!("message {msg}"),
         }));
         let Ok(res) = tokio::time::timeout(Duration::from_secs(10), fut).await else {
             eprintln!("pipe seems full");

pageserver/src/tenant.rs

@@ -11429,11 +11429,11 @@ mod tests {
         if left != right {
             eprintln!("---LEFT---");
             for left in left.iter() {
-                eprintln!("{}", left);
+                eprintln!("{left}");
             }
             eprintln!("---RIGHT---");
             for right in right.iter() {
-                eprintln!("{}", right);
+                eprintln!("{right}");
             }
             assert_eq!(left, right);
         }

rust-toolchain.toml

@@ -1,5 +1,5 @@
 [toolchain]
-channel = "1.87.0"
+channel = "1.88.0"
 profile = "default"
 # The default profile includes rustc, rust-std, cargo, rust-docs, rustfmt and clippy.
 # https://rust-lang.github.io/rustup/concepts/profiles.html