ENH: Fix eCos.cmake to not require a forced compiler

  - Search for libtarget.a explicitly
  - Do not complain about compiler id during try-compile

Modules/Platform/eCos.cmake

@@ -20,27 +20,29 @@ SET(CMAKE_FIND_LIBRARY_SUFFIXES ".a")
 INCLUDE(Platform/UnixPaths)
 
 # eCos can be built only with gcc
-IF(CMAKE_C_COMPILER AND NOT  "${CMAKE_C_COMPILER_ID}" MATCHES "GNU")
+GET_PROPERTY(_IN_TC GLOBAL PROPERTY IN_TRY_COMPILE)
+IF(CMAKE_C_COMPILER AND NOT  "${CMAKE_C_COMPILER_ID}" MATCHES "GNU" AND NOT _IN_TC)
   MESSAGE(FATAL_ERROR "GNU gcc is required for eCos")
-ENDIF(CMAKE_C_COMPILER AND NOT  "${CMAKE_C_COMPILER_ID}" MATCHES "GNU")
-IF(CMAKE_CXX_COMPILER AND NOT  "${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
-  MESSAGE(FATAL_ERROR "GNU gcc is required for eCos")
-ENDIF(CMAKE_CXX_COMPILER AND NOT  "${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
+ENDIF(CMAKE_C_COMPILER AND NOT  "${CMAKE_C_COMPILER_ID}" MATCHES "GNU" AND NOT _IN_TC)
+IF(CMAKE_CXX_COMPILER AND NOT  "${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU" AND NOT _IN_TC)
+  MESSAGE(FATAL_ERROR "GNU g++ is required for eCos")
+ENDIF(CMAKE_CXX_COMPILER AND NOT  "${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU" AND NOT _IN_TC)
 
-# this is a header which is part of every eCos "installation"
-# it would be better to search for libtarget.a, but this isn't possible 
-# at this point in the setup process, since CMAKE_SIZEOF_VOID_P is still
-# unknown, which is used in FIND_LIBRARY()
+# find eCos system files
 FIND_PATH(ECOS_SYSTEM_CONFIG_HEADER_PATH NAMES pkgconf/system.h)
+FIND_LIBRARY(ECOS_SYSTEM_TARGET_LIBRARY NAMES libtarget.a)
 
 IF(NOT ECOS_SYSTEM_CONFIG_HEADER_PATH)
   MESSAGE(FATAL_ERROR "Could not find eCos pkgconf/system.h. Build eCos first and set up CMAKE_FIND_ROOT_PATH correctly.")
 ENDIF(NOT ECOS_SYSTEM_CONFIG_HEADER_PATH)
 
-GET_FILENAME_COMPONENT(ECOS_LIBTARGET_DIRECTORY "${ECOS_SYSTEM_CONFIG_HEADER_PATH}" PATH)
+IF(NOT ECOS_SYSTEM_TARGET_LIBRARY)
+  MESSAGE(FATAL_ERROR "Could not find eCos \"libtarget.a\". Build eCos first and set up CMAKE_FIND_ROOT_PATH correctly.")
+ENDIF(NOT ECOS_SYSTEM_TARGET_LIBRARY)
+
+GET_FILENAME_COMPONENT(ECOS_LIBTARGET_DIRECTORY "${ECOS_SYSTEM_TARGET_LIBRARY}" PATH)
 INCLUDE_DIRECTORIES(${ECOS_SYSTEM_CONFIG_HEADER_PATH})
 ADD_DEFINITIONS(-D__ECOS__=1 -D__ECOS=1)
-SET(ECOS_LIBTARGET_DIRECTORY "${ECOS_LIBTARGET_DIRECTORY}/lib")
 
 # special link commands for eCos executables
 SET(CMAKE_CXX_LINK_EXECUTABLE  "<CMAKE_CXX_COMPILER> <FLAGS> <CMAKE_CXX_LINK_FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> -nostdlib -nostartfiles -L${ECOS_LIBTARGET_DIRECTORY} -Ttarget.ld  <LINK_LIBRARIES>")