[compiler-rt][nsan] Modify NSAN_CFLAGS setting (#98768)

Use -fno-rtti flag to avoid vtables in the runtime library (similarly to asan, dfsan, msan).
Remove unneeded -fPIC from NSAN_CFLAGS.

Fix #98767

Author: chestnykh

compiler-rt/lib/nsan/CMakeLists.txt

@@ -23,11 +23,11 @@ set(NSAN_HEADERS
   nsan_suppressions.h
 )
 
-append_list_if(COMPILER_RT_HAS_FPIC_FLAG -fPIC NSAN_CFLAGS)
-
 set(NSAN_DYNAMIC_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
 
 set(NSAN_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+append_rtti_flag(OFF NSAN_CFLAGS)
+
 set(NSAN_DYNAMIC_CFLAGS ${NSAN_CFLAGS})
 
 set(NSAN_COMMON_RUNTIME_OBJECT_LIBS