class CPUInfo should only be used on Linux to read /proc/cpuinfo contents.
OpenBSD/riscv64 always uses floating-point support.

Index: deps/v8/src/base/cpu.cc
--- deps/v8/src/base/cpu.cc.orig
+++ deps/v8/src/base/cpu.cc
@@ -868,6 +868,8 @@ CPU::CPU()
 #endif  // !USE_SIMULATOR
 
 #elif V8_HOST_ARCH_RISCV64
+
+#if V8_OS_LINUX
   CPUInfo cpu_info;
   char* features = cpu_info.ExtractField("isa");
 
@@ -878,6 +880,14 @@ CPU::CPU()
     has_fpu_ = true;
     has_rvv_ = true;
   }
+
+#elif V8_OS_OPENBSD
+
+  // OpenBSD requires and defaults to FP support.
+  has_fpu_ = true;
+
+#endif  // V8_OS_OPENBSD
+
 #endif  // V8_HOST_ARCH_RISCV64
 }
 
