gcc 4: fix math library fix for genautomata

* The build host's math library is needed, not the host's. Makes a
  difference when build host != host, e.g. when cross-compiling a native
  Haiku compiler on Linux.
* Rename the variable math_library -> build_math_library for clarity.

gcc/gcc/Makefile.in

@@ -3965,7 +3965,7 @@ $(genprogerr:%=build/gen%$(build_exeext)): $(BUILD_ERRORS)
 genprog = $(genprogerr) check checksum condmd
 
 # These programs need libs over and above what they get from the above list.
-build/genautomata$(build_exeext) : BUILD_LIBS += @math_library@
+build/genautomata$(build_exeext) : BUILD_LIBS += @build_math_library@
 
 # These programs are not linked with the MD reader.
 build/gengtype$(build_exeext) : build/gengtype-lex.o build/gengtype-parse.o \

gcc/gcc/configure

@@ -599,7 +599,7 @@ ac_includes_default="\
 #endif"
 
 ac_subst_vars='LTLIBOBJS
-math_library
+build_math_library
 LIBOBJS
 enable_plugin
 pluginlibs
@@ -8849,11 +8849,11 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 # Configure -lm usage for host tools that need it
-math_library="-lm"
-case $host in
+build_math_library="-lm"
+case $build in
   *-*-haiku*)
     # no separate math library needed
-    math_library=
+    build_math_library=
     ;;
 esac
 

gcc/gcc/configure.ac

@@ -1003,11 +1003,11 @@ AC_LANG_POP(C++)
 
 
 # Configure -lm usage for host tools that need it
-math_library="-lm"
-case $host in
+build_math_library="-lm"
+case $build in
   *-*-haiku*)
     # no separate math library needed
-    math_library=
+    build_math_library=
     ;;
 esac