Merge bitcoin/bitcoin#24604: build: fix copypasta in OpenBSD C{XX} flags

28f17c1 build: fix copypasta in OpenBSD C{XX} flags (fanquake)

Pull request description:

  Introduced in #23998.

ACKs for top commit:
  hebasto:
    ACK 28f17c1, I have reviewed the code and it looks OK, not tested on OpenBSD though.

Tree-SHA512: d905161534075f518c8924d3c42cca7ff8d4898e559f1daa9bd03dac95b109b2c3e76790fb8bc65b9e45e8a59566825afbf4dc3734ad74617dfdf797430e486b

Author: fanquake

depends/hosts/openbsd.mk

@@ -1,11 +1,11 @@
 openbsd_CFLAGS=-pipe
-openbsd_CFLAGS_CXXFLAGS=$(openbsd_CFLAGS)
+openbsd_CXXFLAGS=$(openbsd_CFLAGS)
 
-openbsd_CFLAGS_release_CFLAGS=-O2
-openbsd_CFLAGS_release_CXXFLAGS=$(openbsd_release_CFLAGS)
+openbsd_release_CFLAGS=-O2
+openbsd_release_CXXFLAGS=$(openbsd_release_CFLAGS)
 
-openbsd_CFLAGS_debug_CFLAGS=-O1
-openbsd_CFLAGS_debug_CXXFLAGS=$(openbsd_debug_CFLAGS)
+openbsd_debug_CFLAGS=-O1
+openbsd_debug_CXXFLAGS=$(openbsd_debug_CFLAGS)
 
 ifeq (86,$(findstring 86,$(build_arch)))
 i686_openbsd_CC=clang -m32