UBSan warning when fuzzing abs64(...) #20135

When extending the test/fuzz/integer fuzzer I noticed the following UBSan warning when fuzzing abs64(...):

runtime error: negation of -9223372036854775808 cannot be represented in type 'int64_t' (aka 'long'); cast to an unsigned type to negate this value to itself

Fuzzing harness:

diff --git a/src/test/fuzz/integer.cpp b/src/test/fuzz/integer.cpp
index 35d6804d4..bc158e5a2 100644
--- a/src/test/fuzz/integer.cpp
+++ b/src/test/fuzz/integer.cpp
@@ -40,6 +40,8 @@
 #include <set>
 #include <vector>

 void initialize()
 {
     SelectParams(CBaseChainParams::REGTEST);
@@ -82,6 +84,7 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     (void)ComputeMerkleRoot(v256);
     (void)CountBits(u64);
     (void)DecompressAmount(u64);
+    (void)abs64(i64);
     (void)FormatISO8601Date(i64);
     (void)FormatISO8601DateTime(i64);
     // FormatMoney(i) not defined when i == std::numeric_limits<int64_t>::min()

Typically abs(I n) type functions are not defined when n == std::numeric_limits<I>::min() so it could be argued that this is expected, but perhaps the function could be rewritten in a way which guarantees that it gives the same behaviour across systems (instead of UB).