Fix detecting of CPU cores on FreeBSD

On FreeBSD, use the same approach as OS X with `sysctl`.

bin/ruby-build

@@ -115,13 +115,16 @@ file_is_not_empty() {
 }
 
 num_cpu_cores() {
-  local num=""
-  if [ "Darwin" = "$(uname -s)" ]; then
+  local num
+  case "$(uname -s)" in
+  Darwin | *BSD )
     num="$(sysctl -n hw.ncpu 2>/dev/null || true)"
-  elif [ -r /proc/cpuinfo ]; then
-    num="$(grep ^processor /proc/cpuinfo | wc -l)"
-    [ "$num" -gt 0 ] || num=""
-  fi
+    ;;
+  * )
+    num="$(grep ^processor /proc/cpuinfo 2>/dev/null | wc -l | xargs)"
+    num="${num#0}"
+    ;;
+  esac
   echo "${num:-2}"
 }
 

test/build.bats

@@ -245,6 +245,30 @@ make install
 OUT
 }
 
+@test "number of CPU cores is detected on FreeBSD" {
+  cached_tarball "ruby-2.0.0"
+
+  stub uname '-s : echo FreeBSD'
+  stub sysctl '-n hw.ncpu : echo 1'
+  stub_make_install
+
+  export -n MAKE_OPTS
+  run_inline_definition <<DEF
+install_package "ruby-2.0.0" "http://ruby-lang.org/ruby/2.0/ruby-2.0.0.tar.gz"
+DEF
+  assert_success
+
+  unstub uname
+  unstub sysctl
+  unstub make
+
+  assert_build_log <<OUT
+ruby-2.0.0: --prefix=$INSTALL_ROOT
+make -j 1
+make install
+OUT
+}
+
 @test "setting RUBY_MAKE_INSTALL_OPTS to a multi-word string" {
   cached_tarball "ruby-2.0.0"