[compiler-rt] don't use mallopt on musl (PR #101055)

[Daniel Martinez via llvm-commits]

https://github.com/Calandracas606 created https://github.com/llvm/llvm-project/pull/101055

Fixes a build failure on 19.1.0-rc1 when building with musl as the libc

musl does not provide mallopt, whereas glibc does

>From ab03fed23ad6cff13b067e6f401c1144690909bf Mon Sep 17 00:00:00 2001
From: Daniel Martinez <danielmartinez at cock.li>
Date: Mon, 29 Jul 2024 14:15:51 -0400
Subject: [PATCH] don't use mallopt on musl

---
 compiler-rt/lib/nsan/nsan_interceptors.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler-rt/lib/nsan/nsan_interceptors.cpp b/compiler-rt/lib/nsan/nsan_interceptors.cpp
index 544b44f53cc42..baa8185994113 100644
--- a/compiler-rt/lib/nsan/nsan_interceptors.cpp
+++ b/compiler-rt/lib/nsan/nsan_interceptors.cpp
@@ -21,7 +21,7 @@
 
 #include <wchar.h>
 
-#if SANITIZER_LINUX
+#if SANITIZER_LINUX && defined(__GLIBC__)
 extern "C" int mallopt(int param, int value);
 #endif
 
@@ -210,7 +210,7 @@ void __nsan::InitializeInterceptors() {
   CHECK(!initialized);
 
   // Instruct libc malloc to consume less memory.
-#if SANITIZER_LINUX
+#if SANITIZER_LINUX && defined(__GLIBC__)
   mallopt(1, 0);          // M_MXFAST
   mallopt(-3, 32 * 1024); // M_MMAP_THRESHOLD
 #endif