Set module/*headerpath* during bootstrap

Cook also uses module/*headerpath* for finding headers
rather than using module/*syspath*.

Makefile

@@ -133,7 +133,7 @@ build/janet_boot: $(JANET_BOOT_OBJECTS)
 
 # Now the reason we bootstrap in the first place
 build/core_image.c: build/janet_boot
-	build/janet_boot $@ JANET_PATH $(JANET_PATH)
+	build/janet_boot $@ JANET_PATH $(JANET_PATH) JANET_HEADERPATH $(INCLUDEDIR)/janet
 
 ##########################################################
 ##### The main interpreter program and shared object #####
@@ -282,8 +282,8 @@ SONAME=libjanet.so.0
 install: $(JANET_TARGET) build/version.txt
 	mkdir -p $(BINDIR)
 	cp $(JANET_TARGET) $(BINDIR)/janet
-	mkdir -p $(INCLUDEDIR)
-	cp -rf $(JANET_HEADERS) $(INCLUDEDIR)
+	mkdir -p $(INCLUDEDIR)/janet
+	cp -rf $(JANET_HEADERS) $(INCLUDEDIR)/janet
 	mkdir -p $(JANET_PATH)
 	cp -rf $(JANET_HEADERS) $(JANET_PATH)
 	mkdir -p $(LIBDIR)

meson.build

@@ -22,6 +22,7 @@ project('janet', 'c', default_options : ['c_std=c99'])
 
 # Global settings
 janet_path = join_paths(get_option('prefix'), get_option('libdir'), 'janet')
+header_path = join_paths(get_option('prefix'), get_option('includedir'), 'janet')
 
 # Link math library on all systems
 cc = meson.get_compiler('c')
@@ -119,7 +120,7 @@ janet_boot = executable('janet-boot', core_src, boot_src, boot_gen,
 core_image = custom_target('core_image',
   input : [janet_boot],
   output : 'core_image.gen.c',
-  command : [janet_boot, '@OUTPUT@', 'JANET_PATH', janet_path])
+  command : [janet_boot, '@OUTPUT@', 'JANET_PATH', janet_path, 'JANET_HEADERPATH', header_path])
 
 libjanet = shared_library('janet', core_src, core_image,
   include_directories : incdir,
@@ -169,10 +170,8 @@ run_target('repl', command : [janet_mainclient])
 
 # Installation
 install_man('janet.1')
-install_headers('src/include/janet.h', 'src/include/janetconf.h')
+install_headers('src/include/janet.h', 'src/include/janetconf.h', subdir: 'janet')
 janet_libs = [
-  'src/include/janet.h',
-  'src/include/janetconf.h',
   'tools/bars.janet',
   'tools/cook.janet',
   'tools/highlight.janet'

src/boot/boot.janet

@@ -1597,6 +1597,11 @@
   on Windows is C:/Janet/Library."
   (or (process/opts "JANET_PATH") ""))
 
+(var module/*headerpath*
+  "The path where the janet headers are installed. Useful for building
+  native modules or compiling code at runtime."
+  (process/opts "JANET_HEADERPATH"))
+
 # Version of fexists that works even with a reduced OS
 (if-let [has-stat (_env 'os/stat)]
   (let [stat (has-stat :value)]

tools/cook.janet

@@ -103,7 +103,7 @@
                   (if is-mac " -undefined dynamic_lookup" ""))))
 (def CFLAGS (string
               (if is-win "/I" "-I")
-              module/*syspath*
+              module/*headerpath*
               (if is-win " /O" " -std=c99 -Wall -Wextra -fpic -O")
               OPTIMIZE))