[SOL] Set default visibility of symbols in SBF binaries to hidden

Make a solana specific version of __rdl_oom handler that doesn't use a
static variable.  This variable can't be supported is Solana execution
environment.

Author: dmakarov

compiler/rustc_target/src/spec/sbf_base.rs

@@ -36,6 +36,7 @@ SECTIONS
     TargetOptions {
         allow_asm: true,
         c_int_width: "64".into(),
+        default_hidden_visibility: true,
         dll_prefix: "".into(),
         dynamic_linking: true,
         eh_frame_header: false,

library/alloc/src/alloc.rs

@@ -425,6 +425,7 @@ pub mod __alloc_error_handler {
     // called via generated `__rust_alloc_error_handler` if there is no
     // `#[alloc_error_handler]`.
     #[rustc_std_internal_symbol]
+    #[cfg(not(target_family = "solana"))]
     pub unsafe fn __rdl_oom(size: usize, _align: usize) -> ! {
         extern "Rust" {
             // This symbol is emitted by rustc next to __rust_alloc_error_handler.
@@ -441,4 +442,12 @@ pub mod __alloc_error_handler {
             )
         }
     }
+
+    #[rustc_std_internal_symbol]
+    #[cfg(target_family = "solana")]
+    pub unsafe fn __rdl_oom(size: usize, _align: usize) -> ! {
+        core::panicking::panic_nounwind_fmt(format_args!(
+            "memory allocation of {size} bytes failed"
+        ))
+    }
 }