[msan] Increase kNumStackOriginDescrs constant (#92838)

This increases the constant size of kNumStackOriginDescrs to 4M (64GB of
BSS across two arrays), which ought to be enough for anybody.

This is the easier alternative suggested by eugenis@ in
#92826.

compiler-rt/lib/msan/msan.cpp

@@ -100,7 +100,11 @@ int msan_report_count = 0;
 
 // Array of stack origins.
 // FIXME: make it resizable.
-static const uptr kNumStackOriginDescrs = 1024 * 1024;
+// Although BSS memory doesn't cost anything until used, it is limited to 2GB
+// in some configurations (e.g., "relocation R_X86_64_PC32 out of range:
+// ... is not in [-2147483648, 2147483647]; references section '.bss'").
+// We use kNumStackOriginDescrs * (sizeof(char*) + sizeof(uptr)) == 64MB.
+static const uptr kNumStackOriginDescrs = 4 * 1024 * 1024;
 static const char *StackOriginDescr[kNumStackOriginDescrs];
 static uptr StackOriginPC[kNumStackOriginDescrs];
 static atomic_uint32_t NumStackOriginDescrs;