move build to build3 to avoid naming conflict with Bullet 2.x

fix build error in BasicGpuDemo
Thanks to joen66 for the report here:
https://github.com/erwincoumans/bullet3/issues/5

build3/stringifyKernel.lua

@@ -0,0 +1,79 @@
+
+
+function stringifyKernel(filenameIn, filenameOut, kernelMethod)
+  local BUFSIZE = 1024*1024     -- 1MB
+	local f = io.open(filenameIn,"r");
+   	local fw = io.open(filenameOut,"w");
+   	fw:write("//this file is autogenerated using stringify.bat (premake --stringify) in the build folder of this project\n")
+   	fw:write("static const char* " .. kernelMethod .. "= \\\n")
+    local cc, lc, wc = 0, 0, 0   -- char, line, and word counts
+    while true do
+      local lines, rest = f:read(BUFSIZE, "*line")
+      if not lines then break end
+      
+      local i = 0
+      local startpos = 0
+      local slen = string.len(lines)
+      local endpos = 0
+    	while true do
+      	i = string.find(lines, "\n", i+1)    -- find 'next' newline
+      	if i == nil then 
+      		endpos = slen
+      	else
+      	  endpos = i
+      	end
+      	oneline = string.sub(lines,startpos,endpos)
+      	oneline = string.gsub(oneline,"\n","")
+	oneline = string.gsub(oneline,"\"","\\\"");
+      	oneline = '\"' .. oneline .. '\\n\"'
+      	oneline = string.gsub(oneline,"\\\\n","")
+      	oneline = oneline .. "\n"
+      	--print(oneline)
+      	fw:write(oneline)
+      	if i == nil then break end
+      	startpos = i+1
+      end
+      
+      if rest then lines = lines .. rest .. '\n' end
+      cc = cc + string.len(lines)
+      -- count words in the chunk
+      local _,t = string.gsub(lines, "%S+", "")
+      wc = wc + t
+      -- count newlines in the chunk
+      _,t = string.gsub(lines, "\n", "\n")
+      lc = lc + t
+    end
+    --print("stringified " .. filenameIn .. " into " .. filenameOut .. " processed " .. lc .. " lines")
+    print(filenameIn .. " (" .. lc .. " lines)")
+
+ 		f:close()
+ 		fw:write(";\n")
+ 		fw:close()
+ end
+ 
+ newoption {
+    trigger     = "kernelfile",
+    value				=	"kernelpath",
+    description = "full path to the kernel source input file"
+  }
+
+ newoption {
+    trigger     = "headerfile",
+    value				=	"path",
+    description = "full path to the header output file"
+  }
+
+ newoption {
+    trigger     = "stringname",
+    value				=	"var",
+    description = "name of the kernel string variable"
+  }
+  
+ newaction {
+   trigger     = "stringify",
+   description = "stringify kernels source code into strings",
+   execute = function ()
+    stringifyKernel( _OPTIONS["kernelfile"] , _OPTIONS["headerfile"], _OPTIONS["stringname"])    
+ 
+   end
+}