patch allows user to define 2 additional, optional parameters in the preferences.txt file.

the parameters allow to tweak the default linker settings by injecting custom options to the avr-gcc command line.
the parameters:
* build.linker_options - specified options will *replace* the default '-Wl,--gc-sections' options
* build.linker_additional_options - options will *replace* the default '-lm' (at the end of the command line)

fine tuning these variables allows one to link against the float-enabled versions of printf and scanf.

has been tested on windows XP, with the following options set in the user's preferences.txt:
<pre>
build.linker_options=-Wl,-u,vfprintf,-u,vfscanf,--gc-sections
build.linker_additional_options=-lprintf_flt -lscanf_flt -lm
</pre>

Author: srejbi

app/src/processing/app/debug/Compiler.java

@@ -196,7 +196,8 @@ public boolean compile(Sketch sketch,
     List baseCommandLinker = new ArrayList(Arrays.asList(new String[] {
       avrBasePath + "avr-gcc",
       "-Os",
-      "-Wl,--gc-sections"+optRelax,
+      (Preferences.get("build.linker_options")!= null ? Preferences.get("build.linker_options")+optRelax :
+      "-Wl,--gc-sections"+optRelax),
       "-mmcu=" + boardPreferences.get("build.mcu"),
       "-o",
       buildPath + File.separator + primaryClassName + ".elf"
@@ -208,8 +209,14 @@ public boolean compile(Sketch sketch,
 
     baseCommandLinker.add(runtimeLibraryName);
     baseCommandLinker.add("-L" + buildPath);
-    baseCommandLinker.add("-lm");
-
+    if (Preferences.get("build.linker_additional_options") != null) {
+        for (String addopt : Preferences.get("build.linker_additional_options").split(" ")) {
+        	baseCommandLinker.add(addopt);
+        }
+    } else {
+      baseCommandLinker.add("-lm");
+    }
+    
     execAsynchronously(baseCommandLinker);
 
     List baseCommandObjcopy = new ArrayList(Arrays.asList(new String[] {