Use relative paths in apply_incpaths by default

Relative paths are usually best for for specialized compilers (emscripten),
so this is for convenience. Absolute paths are usually faster.

ChangeLog

@@ -27,4 +27,5 @@ NEW IN WAF 1.9
   - Remove Utils.nogc
   - Modify Utils.run_once so that it accepts a list of *args
   - Improve the task consumer in Runner.py
+  - Use relative paths in apply_incpaths by default (and absolute ones when paths cross drives)
 

TODO

@@ -4,7 +4,6 @@ Waf 1.9
 * Better consistency between check_cfg and check_cc variables
 * Let more context commands depend on the configuration
 * Rework qt5
-* Use relative paths in apply_incpaths (and absolute ones when paths cross drives)
 * Regexps for extension-based processing
 * Other issues listed on https://github.com/waf-project/waf/issues
 

waflib/Tools/ccroot.py

@@ -120,7 +120,7 @@ def apply_incpaths(self):
 
 	lst = self.to_incnodes(self.to_list(getattr(self, 'includes', [])) + self.env['INCLUDES'])
 	self.includes_nodes = lst
-	self.env['INCPATHS'] = [x.abspath() for x in lst]
+	self.env['INCPATHS'] = [x.path_from(self.bld.bldnode) for x in lst]
 
 class link_task(Task.Task):
 	"""

waflib/extras/c_emscripten.py

@@ -82,16 +82,3 @@ def configure(conf):
 	conf.env.cxxprogram_PATTERN = '%s.html'
 	conf.env.append_value('LINKFLAGS',['-Wl,--enable-auto-import'])
 
-@feature('c', 'cxx', 'acm', 'includes')
-@after_method('propagate_uselib_vars', 'process_source', 'apply_incpaths')
-def apply_incpaths_emscripten(self):
-	"""
-	Emscripten doesn't like absolute include paths
-	"""
-	# TODO: in waf 1.9 we can switch back to bldnode as the default since path_from handles cross-drive paths
-	if self.env.CC_NAME != 'emscripten' or self.env.CC_NAME != 'emscripten':
-		return
-	lst = self.to_incnodes(self.to_list(getattr(self, 'includes', [])) + self.env['INCLUDES'])
-	self.includes_nodes = lst
-	self.env['INCPATHS'] = [x.path_from(self.bld.bldnode) for x in lst]
-