[compiler-rt] [lsan] Fix free(NULL) interception during initialization (PR #106912)

[Vitaly Buka via llvm-commits]

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@@ -77,6 +77,8 @@ INTERCEPTOR(void*, malloc, uptr size) {
 }
 
 INTERCEPTOR(void, free, void *p) {
+  if (!p)
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vitalybuka wrote:

this will fix only lsan

to fix all, I propose to change 
`DlsymAlloc::PointerIsMine` to return true for NULL
and teach `DlsymAlloc::Free` to handle it correctly

https://github.com/llvm/llvm-project/pull/106912