c99 on android

configure.ac

@@ -245,8 +245,18 @@ AC_SUBST(CARES_SYMBOL_HIDING_CFLAG)
 
 
 if test "$enable_warnings" = "yes"; then
-  AX_APPEND_COMPILE_FLAGS([-std=c90 -Wall -Wextra -Waggregate-return -Wcast-align -Wcast-qual -Wconversion -Wdeclaration-after-statement -Wdouble-promotion -Wfloat-equal -Wformat-security -Winit-self -Wjump-misses-init -Wlogical-op -Wmissing-braces -Wmissing-declarations -Wmissing-format-attribute -Wmissing-include-dirs -Wmissing-prototypes -Wnested-externs -Wno-coverage-mismatch -Wold-style-definition -Wpacked -Wpedantic -Wpointer-arith -Wredundant-decls -Wshadow -Wsign-conversion -Wstrict-overflow -Wstrict-prototypes -Wtrampolines -Wundef -Wunreachable-code -Wunused -Wvariadic-macros -Wvla -Wwrite-strings -Werror=implicit-int -Werror=implicit-function-declaration -Werror=partial-availability -Wno-long-long ],
+  AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -Waggregate-return -Wcast-align -Wcast-qual -Wconversion -Wdeclaration-after-statement -Wdouble-promotion -Wfloat-equal -Wformat-security -Winit-self -Wjump-misses-init -Wlogical-op -Wmissing-braces -Wmissing-declarations -Wmissing-format-attribute -Wmissing-include-dirs -Wmissing-prototypes -Wnested-externs -Wno-coverage-mismatch -Wold-style-definition -Wpacked -Wpedantic -Wpointer-arith -Wredundant-decls -Wshadow -Wsign-conversion -Wstrict-overflow -Wstrict-prototypes -Wtrampolines -Wundef -Wunreachable-code -Wunused -Wvariadic-macros -Wvla -Wwrite-strings -Werror=implicit-int -Werror=implicit-function-declaration -Werror=partial-availability -Wno-long-long ],
     [AM_CFLAGS], [-Werror])
+
+  dnl Android requires c99, all others should use c90
+  case $host_os in
+    *android*)
+      AX_APPEND_COMPILE_FLAGS([-std=c99], [AM_CFLAGS], [-Werror])
+      ;;
+    *)
+      AX_APPEND_COMPILE_FLAGS([-std=c90], [AM_CFLAGS], [-Werror])
+      ;;
+  esac
 fi
 
 if test "$ax_cv_c_compiler_vendor" = "intel"; then