doxygen input needs HIP_PATH environment variable

Change-Id: I05e027b765fde6339693564bb9dcc584a4ce43bd

docs/Makefile

@@ -2,4 +2,4 @@ HIP_PATH ?= ..
 DOXYGEN_SRC=$(wildcard $(HIP_PATH)/include/hcc_detail/*.h) $(wildcard $(HIP_PATH)/include/*.h) $(HIP_PATH)/src/hip_hcc.cpp $(wildcard doxygen-input/*)
 
 doc:  $(DOXYGEN_SRC)
-	doxygen doxygen-input/doxy.cfg
+	HIP_PATH=$(HIP_PATH) doxygen doxygen-input/doxy.cfg

docs/doxygen-input/doxy.cfg

@@ -758,9 +758,11 @@ WARN_LOGFILE           =
 # spaces.
 # Note: If this tag is empty the current directory is searched.
 
-#INPUT                  = README.dox include/hip_kalmar.h include/hip_kalmar_texture.h 
-INPUT                  = doxygen-input/mainpage.txt doxygen-input/sync.txt \
-                        ../include/  ../include/hcc_detail/ ../src/
+INPUT                  = $(HIP_PATH)/docs/doxygen-input/mainpage.txt \
+                         $(HIP_PATH)/docs/doxygen-input/sync.txt \
+                         $(HIP_PATH)/include/ \
+                         $(HIP_PATH)/include/hcc_detail/ \
+                         $(HIP_PATH)/src/
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
@@ -848,7 +850,7 @@ EXAMPLE_RECURSIVE      = NO
 # that contain images that are to be included in the documentation (see the
 # \image command).
 
-IMAGE_PATH             = doxygen-input/images
+IMAGE_PATH             = $(HIP_PATH)/docs/doxygen-input/images
 
 # The INPUT_FILTER tag can be used to specify a program that doxygen should
 # invoke to filter for each input file. Doxygen will invoke the filter program
@@ -896,7 +898,7 @@ FILTER_SOURCE_PATTERNS =
 # (index.html). This can be useful if you have a project on for instance GitHub
 # and want to reuse the introduction page also for the doxygen output.
 
-USE_MDFILE_AS_MAINPAGE = ../README.md
+USE_MDFILE_AS_MAINPAGE = $(HIP_PATH)/README.md
 
 #---------------------------------------------------------------------------
 # Configuration options related to source browsing