Powerpc has extended double that doesn't match x86 coding. Power format would
need special tests to verify correctness but for now it is enough to prevent
incorrect test from running.

Index: llvm-toolchain-snapshot_8~svn342269/libcxxabi/test/test_demangle.pass.cpp
===================================================================
--- llvm-toolchain-snapshot_8~svn342269.orig/libcxxabi/test/test_demangle.pass.cpp
+++ llvm-toolchain-snapshot_8~svn342269/libcxxabi/test/test_demangle.pass.cpp
@@ -29797,7 +29797,7 @@ const char* invalid_cases[] =
     "NSoERj5E=Y1[uM:ga",
     "Aon_PmKVPDk7?fg4XP5smMUL6;<WsI_mgbf23cCgsHbT<l8EE\0uVRkNOoXDrgdA4[8IU>Vl<>IL8ayHpiVDDDXTY;^o9;i",
     "_ZNSt16allocator_traitsISaIN4llvm3sys2fs18directory_iteratorEEE9constructIS3_IS3_EEEDTcl12_S_constructfp_fp0_spcl7forwardIT0_Efp1_EEERS4_PT_DpOS7_",
-#if !LDBL_FP80
+#if !LDBL_FP80 && __LDBL_MANT_DIG__ < 64
     "_ZN5test01hIfEEvRAcvjplstT_Le4001a000000000000000E_c",
 #endif
 	// The following test cases were found by libFuzzer+ASAN