Merge branch 'master' into codesourcery.

All Matt's advices applied.

target.mk

@@ -1,5 +1,5 @@
-MACHINE		= mips
-DESTDIR		?= $(TOPSRC)
+MACHINE     = mips
+DESTDIR     ?= $(TOPSRC)
 RELEASE     = 0.0
 BUILD       = $(shell git rev-list HEAD --count)
 VERSION     = $(RELEASE)-$(BUILD)
@@ -22,30 +22,40 @@ endif
 # MPLABX C32 compiler doesn't support some functionality
 # we need, so use chipKIT compiler by default.
 ifndef GCCPREFIX
+ifeq (/usr/local/pic32-tools/bin/pic32-gcc,$(wildcard /usr/local/pic32-tools/bin/pic32-gcc))
     GCCPREFIX   = /usr/local/pic32-tools/bin/pic32-
     LDFLAGS     = -Wl,--oformat=elf32-tradlittlemips
     INCLUDES    = -I/usr/local/pic32-tools/lib/gcc/pic32mx/4.5.1/include
 endif
+endif
 
 # Generic MIPS toolchain
 # ~~~~~~~~~~~~~~~~~~~~~~
 # You can build it from sources, as described on page
 # http://retrobsd.org/wiki/doku.php/doc/toolchain-mips
 ifndef GCCPREFIX
+ifeq (/usr/local/mips-gcc-4.7.2/bin/mips-elf-gcc,$(wildcard /usr/local/mips-gcc-4.7.2/bin/mips-elf-gcc))
     GCCPREFIX   = /usr/local/mips-gcc-4.7.2/bin/mips-elf-
     LDFLAGS     =
     INCLUDES    =
 endif
+endif
 
 # Mentor Sourcery CodeBench Lite toolchain
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 # You can download a Linux or Windows binary package from
 # https://sourcery.mentor.com/GNUToolchain/release2641
 ifndef GCCPREFIX
+ifeq (/usr/local/mips-2013.11/bin/mips-sde-elf-gcc,$(wildcard /usr/local/mips-2013.11/bin/mips-sde-elf-gcc))
     GCCPREFIX   = /usr/local/mips-2013.11/bin/mips-sde-elf-
     LDFLAGS     = -Wl,--oformat=elf32-tradlittlemips
     INCLUDES    =
 endif
+endif
+
+ifndef GCCPREFIX
+    $(error Unable to locate any GCC MIPS toolchain!)
+endif
 
 CC		= $(GCCPREFIX)gcc -mips32r2 -EL -msoft-float -nostdinc -fshort-double -I$(TOPSRC)/include $(INCLUDES)
 CXX             = $(GCCPREFIX)g++ -mips32r2 -EL -msoft-float -nostdinc -fshort-double -I$(TOPSRC)/include $(INCLUDES)