Install only 1 copy, not 2 copies, of osx headers.

Before this commit, the headers in plat/osx/include got installed
twice into PLATIND/osx386/include and PLATIND/osxppc/include.  This
commit installs them once into PLATIND/osx/include and changes both
descr files to find them.

Several rules in lang/ depend on plat/osx386/include+headers or
plat/osxppc/include+headers.  They each become a simplerule that
depends on plat/osx/include+headers.

plat/osx/include/build.lua

@@ -0,0 +1,24 @@
+include("plat/build.lua")
+
+headermap = {}
+packagemap = {}
+
+local function addheader(h)
+	headermap[h] = "plat/osx/include/"..h
+	packagemap["$(PLATIND)/osx/include/"..h] = "plat/osx/include/"..h
+end
+
+addheader("ack/config.h")
+addheader("sys/mman.h")
+addheader("sys/types.h")
+addheader("unistd.h")
+
+acklibrary {
+	name = "headers",
+	hdrs = headermap
+}
+
+installable {
+	name = "pkg",
+	map = packagemap
+}

plat/osx386/build-pkg.lua

@@ -17,7 +17,7 @@ installable {
 	map = {
 		"+tools",
 		"+libs",
-		"./include+pkg",
+		"plat/osx/include+pkg",
 		["$(PLATIND)/osx386/boot.o"] = "+boot",
 		["$(PLATIND)/osx386/libsys.a"] = "./libsys+lib",
 	}

plat/osx386/descr

@@ -29,7 +29,7 @@ var EGO_PLAT_FLAGS=-M{EM}/share/ack/ego/{ARCH}.descr
 # Override the setting in fe so that files compiled for osx386 can see
 # the platform-specific headers.
 
-var C_INCLUDES=-I{PLATFORMDIR}/include -I{EM}/share/ack/include/ansi
+var C_INCLUDES=-I{EM}/share/ack/osx/include -I{EM}/share/ack/include/ansi
 
 name be
 	from .m.g

plat/osx386/include/build.lua

@@ -1,24 +1,7 @@
-include("plat/build.lua")
-
-headermap = {}
-packagemap = {}
-
-local function addheader(h)
-	headermap[h] = "plat/osx/include/"..h
-	packagemap["$(PLATIND)/osx386/include/"..h] = "plat/osx/include/"..h
-end
-
-addheader("ack/config.h")
-addheader("sys/mman.h")
-addheader("sys/types.h")
-addheader("unistd.h")
-
-acklibrary {
+simplerule {
 	name = "headers",
-	hdrs = headermap
-}
-
-installable {
-	name = "pkg",
-	map = packagemap
+	deps = { "plat/osx/include+headers" },
+	ins = {},
+	outs = {},
+	commands = {},
 }

plat/osxppc/build-pkg.lua

@@ -17,7 +17,7 @@ installable {
 	map = {
 		"+tools",
 		"+libs",
-		"./include+pkg",
+		"plat/osx/include+pkg",
 		["$(PLATIND)/osxppc/boot.o"] = "+boot",
 		["$(PLATIND)/osxppc/libsys.a"] = "./libsys+lib",
 	}

plat/osxppc/descr

@@ -30,7 +30,7 @@ var MACHOPT_F=-m10
 # Override the setting in fe so that files compiled for osxppc can see
 # the platform-specific headers.
 
-var C_INCLUDES=-I{PLATFORMDIR}/include -I{EM}/share/ack/include/ansi
+var C_INCLUDES=-I{EM}/share/ack/osx/include -I{EM}/share/ack/include/ansi
 
 name be
 	from .m.g

plat/osxppc/include/build.lua

@@ -1,24 +1,7 @@
-include("plat/build.lua")
-
-headermap = {}
-packagemap = {}
-
-local function addheader(h)
-	headermap[h] = "plat/osx/include/"..h
-	packagemap["$(PLATIND)/osxppc/include/"..h] = "plat/osx/include/"..h
-end
-
-addheader("ack/config.h")
-addheader("sys/mman.h")
-addheader("sys/types.h")
-addheader("unistd.h")
-
-acklibrary {
+simplerule {
 	name = "headers",
-	hdrs = headermap
-}
-
-installable {
-	name = "pkg",
-	map = packagemap
+	deps = { "plat/osx/include+headers" },
+	ins = {},
+	outs = {},
+	commands = {},
 }