src: mv ../buildEnvironmentVariables mkhdr

Also note that the file must be valid shell and mk input.
For #321.

src/mkenv

@@ -0,0 +1,22 @@
+# This file must be valid mk input for mkhdr
+# and also valid shell input for ../dist/buildmk
+
+SYSNAME=`uname`
+OBJTYPE=`(uname -m -p 2>/dev/null || uname -m) | sed '
+	s;.*i[3-6]86.*;386;;
+	s;.*i86pc.*;386;;
+	s;.*amd64.*;x86_64;;
+	s;.*x86_64.*;x86_64;;
+	s;.*armv.*;arm;g;
+	s;.*powerpc.*;power;g;
+	s;.*PowerMacintosh.*;power;g;
+	s;.*Power.Macintosh.*;power;g;
+	s;.*macppc.*;power;g;
+	s;.*mips.*;mips;g;
+	s;.*ppc64.*;power;g;
+	s;.*ppc.*;power;g;
+	s;.*alpha.*;alpha;g;
+	s;.*sun4u.*;sun4u;g;
+	s;.*aarch64.*;arm64;
+	s;.*arm64.*;arm64;
+'`

src/mkhdr

@@ -1,4 +1,4 @@
-<$PLAN9/buildEnvironmentVariables
+<$PLAN9/src/mkenv
 
 BIN=$PLAN9/bin
 LIBDIR=$PLAN9/lib