Bug 1122785 - Detect the extension for executables when configuring; r=glandium

This is required for cross-compiles with MSVC on Linux, otherwise
the compiler sanity checks fail because ${ac_exeext} is empty.

configure.in

@@ -10,6 +10,7 @@ dnl ========================================================
 AC_PREREQ(2.13)
 AC_INIT(config/config.mk)
 AC_CONFIG_AUX_DIR(${srcdir}/build/autoconf)
+AC_EXEEXT
 AC_CANONICAL_SYSTEM
 TARGET_CPU="${target_cpu}"
 TARGET_VENDOR="${target_vendor}"

js/src/configure.in

@@ -10,6 +10,7 @@ dnl ========================================================
 AC_PREREQ(2.13)
 AC_INIT(js/src/jsapi.h)
 AC_CONFIG_AUX_DIR(${srcdir}/build/autoconf)
+AC_EXEEXT
 AC_CANONICAL_SYSTEM
 TARGET_CPU="${target_cpu}"
 TARGET_VENDOR="${target_vendor}"