[libc] Add noexcept to aligned_alloc declaration in full-build mode (#191236)

The extern "C" declaration of aligned_alloc in the proxy header lacked a
noexcept specifier, producing warnings when compiled as C++. Added a
__cplusplus guard so C++ gets noexcept while C compilation remains
unaffected.

libc/hdr/func/aligned_alloc.h

@@ -10,8 +10,13 @@
 #define LLVM_LIBC_HDR_FUNC_ALIGNED_ALLOC_H
 
 #ifdef LIBC_FULL_BUILD
+
 #include "hdr/types/size_t.h"
-extern "C" void *aligned_alloc(size_t, size_t);
+#include "include/__llvm-libc-common.h"
+
+__BEGIN_C_DECLS
+void *aligned_alloc(size_t, size_t) __NOEXCEPT;
+__END_C_DECLS
 
 #else // Overlay mode
 

libc/hdr/func/free.h

@@ -11,7 +11,11 @@
 
 #ifdef LIBC_FULL_BUILD
 
-extern "C" void free(void *) noexcept;
+#include "include/__llvm-libc-common.h"
+
+__BEGIN_C_DECLS
+void free(void *) __NOEXCEPT;
+__END_C_DECLS
 
 #else // Overlay mode
 

libc/hdr/func/malloc.h

@@ -12,8 +12,11 @@
 #ifdef LIBC_FULL_BUILD
 
 #include "hdr/types/size_t.h"
+#include "include/__llvm-libc-common.h"
 
-extern "C" void *malloc(size_t) noexcept;
+__BEGIN_C_DECLS
+void *malloc(size_t) __NOEXCEPT;
+__END_C_DECLS
 
 #else // Overlay mode
 

libc/hdr/func/realloc.h

@@ -12,8 +12,11 @@
 #ifdef LIBC_FULL_BUILD
 
 #include "hdr/types/size_t.h"
+#include "include/__llvm-libc-common.h"
 
-extern "C" void *realloc(void *ptr, size_t new_size) noexcept;
+__BEGIN_C_DECLS
+void *realloc(void *ptr, size_t new_size) __NOEXCEPT;
+__END_C_DECLS
 
 #else // Overlay mode