fix: protobuf install in build (#2714)

Co-authored-by: Michael Neale <michael.neale@gmail.com>

Cross.toml

@@ -1,4 +1,11 @@
 # Configuration for cross-compiling using cross
+[build.env]
+passthrough = [
+    "PROTOC",
+    "RUST_LOG",
+    "RUST_BACKTRACE"
+]
+
 [target.aarch64-unknown-linux-gnu]
 xargo = false
 pre-build = [
@@ -6,29 +13,62 @@ pre-build = [
     "dpkg --add-architecture arm64",
     """\
     apt-get update --fix-missing && apt-get install -y \
+     curl \
+     unzip \
      pkg-config \
      libssl-dev:arm64 \
      libdbus-1-dev:arm64 \
      libxcb1-dev:arm64
+    """,
+    """\
+    curl -LO https://github.com/protocolbuffers/protobuf/releases/download/v31.1/protoc-31.1-linux-x86_64.zip && \
+    unzip -o protoc-31.1-linux-x86_64.zip -d /usr/local && \
+    chmod +x /usr/local/bin/protoc && \
+    ln -sf /usr/local/bin/protoc /usr/bin/protoc && \
+    which protoc && \
+    protoc --version
     """
 ]
 
 [target.x86_64-unknown-linux-gnu]
 xargo = false
 pre-build = [
-    # Install necessary dependencies for x86_64
-    # We don't need architecture-specific flags because x86_64 dependencies are installable on Ubuntu system
     """\
     apt-get update && apt-get install -y \
+     curl \
+     unzip \
      pkg-config \
      libssl-dev \
      libdbus-1-dev \
-     libxcb1-dev \
+     libxcb1-dev
+    """,
+    """\
+    curl -LO https://github.com/protocolbuffers/protobuf/releases/download/v31.1/protoc-31.1-linux-x86_64.zip && \
+    unzip -o protoc-31.1-linux-x86_64.zip -d /usr/local && \
+    chmod +x /usr/local/bin/protoc && \
+    ln -sf /usr/local/bin/protoc /usr/bin/protoc && \
+    which protoc && \
+    protoc --version
     """
 ]
+env = { "PROTOC" = "/usr/bin/protoc", "PATH" = "/usr/local/bin:${PATH}" }
 
 [target.x86_64-pc-windows-gnu]
 image = "dockcross/windows-static-x64:latest"
 # Enable verbose output for Windows builds
 build-std = true
 env = { "RUST_LOG" = "debug", "RUST_BACKTRACE" = "1", "CROSS_VERBOSE" = "1" }
+pre-build = [
+    """\
+    apt-get update && apt-get install -y \
+     curl \
+     unzip
+    """,
+    """\
+    curl -LO https://github.com/protocolbuffers/protobuf/releases/download/v31.1/protoc-31.1-linux-x86_64.zip && \
+    unzip protoc-31.1-linux-x86_64.zip -d /usr/local && \
+    chmod +x /usr/local/bin/protoc && \
+    export PROTOC=/usr/local/bin/protoc && \
+    protoc --version
+    """
+]