Build with Clang on OpenBSD

This is the default compiler starting with OpenBSD 6.2, and has been
installed by default on OpenBSD since 6.0.

Make.inc

@@ -24,12 +24,7 @@ endif
 USEGCC = 1
 USECLANG = 0
 
-ifeq ($(OS), Darwin)
-USEGCC = 0
-USECLANG = 1
-endif
-
-ifeq ($(OS), FreeBSD)
+ifneq (,$(findstring $(OS),Darwin FreeBSD OpenBSD))
 USEGCC = 0
 USECLANG = 1
 endif

README.md

@@ -16,24 +16,20 @@ consistently across compilers and operating systems, and in 32-bit and
 
 OpenLibm builds on Linux, Mac OS X, Windows, FreeBSD, OpenBSD, and DragonFly BSD.
 It builds with both GCC and clang. Although largely tested and widely
-used on x86 architectures, openlibm also supports ARM and
-powerPC.
+used on x86 architectures, OpenLibm also supports ARM and
+PowerPC.
 
 ## Build instructions
 
-1. Use `make` to build OpenLibm.
+1. Use GNU Make to build OpenLibm. This is `make` on most systems, but `gmake` on BSDs.
 2. Use `make USEGCC=1` to build with GCC. This is the default on
    Linux and Windows.
-3. Use `make USECLANG=1` to build with clang. This is the default on OS X
-   and FreeBSD.
+3. Use `make USECLANG=1` to build with clang. This is the default on OS X, FreeBSD,
+   and OpenBSD.
 4. Architectures are auto-detected. Use `make ARCH=i386` to force a
    build for i386. Other supported architectures are i486, i586, and
    i686. GCC 4.8 is the minimum requirement for correct codegen on
    older 32-bit architectures.
-5. On OpenBSD, you need to install GNU Make (port name: `gmake`) and a recent
-   version of `gcc` (tested: 4.9.2), as the default version provided by OpenBSD
-   is too old (4.2.1). If you use OpenBSD's port system for this (port name:
-   `gcc`), run `make CC=egcc` to force Make to use the newer `gcc`.
 
 ## Acknowledgements