diff --git a/build_tools/build_detect_platform b/build_tools/build_detect_platform
index 7b18a5d5f..00fa2b264 100755
--- a/build_tools/build_detect_platform
+++ b/build_tools/build_detect_platform
@@ -533,7 +533,7 @@ if test "$USE_HDFS"; then
   JAVA_LDFLAGS="$JAVA_LDFLAGS $HDFS_LDFLAGS"
 fi
 
-if test -z "$PORTABLE"; then
+if test "0$PORTABLE" -eq 0; then
   if test -n "`echo $TARGET_ARCHITECTURE | grep ^ppc64`"; then
     # Tune for this POWER processor, treating '+' models as base models
     POWER=`LD_SHOW_AUXV=1 /bin/true | grep AT_PLATFORM | grep -E -o power[0-9]+`
@@ -547,16 +547,34 @@ if test -z "$PORTABLE"; then
     COMMON_FLAGS="$COMMON_FLAGS"
   elif [ "$TARGET_OS" == "IOS" ]; then
     COMMON_FLAGS="$COMMON_FLAGS"
-  elif [ "$TARGET_OS" != "AIX" ] && [ "$TARGET_OS" != "SunOS" ]; then
+  elif [ "$TARGET_OS" == "AIX" ] || [ "$TARGET_OS" == "SunOS" ]; then
+    # TODO: Not sure why we don't use -march=native on these OSes
+    if test "$USE_SSE"; then
+      TRY_SSE_ETC="1"
+    fi
+  else
     COMMON_FLAGS="$COMMON_FLAGS -march=native "
-  elif test "$USE_SSE"; then
-    COMMON_FLAGS="$COMMON_FLAGS -msse4.2 -mpclmul"
   fi
-elif test "$USE_SSE"; then
-  COMMON_FLAGS="$COMMON_FLAGS -msse4.2 -mpclmul"
+else
+  # PORTABLE=1
+  if test "$USE_SSE"; then
+    TRY_SSE_ETC="1"
+  fi
 fi
 
-$CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS -x c++ - -o /dev/null 2>/dev/null <<EOF
+if test "$TRY_SSE_ETC"; then
+  # The USE_SSE flag now means "attempt to compile with widely-available
+  # Intel architecture extensions utilized by specific optimizations in the
+  # source code." It's a qualifier on PORTABLE=1 that means "mostly portable."
+  # It doesn't even really check that your current CPU is compatible.
+  #
+  # SSE4.2 available since nehalem, ca. 2008-2010
+  TRY_SSE42="-msse4.2"
+  # PCLMUL available since westmere, ca. 2010-2011
+  TRY_PCLMUL="-mpclmul"
+fi
+
+$CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS $TRY_SSE42 -x c++ - -o /dev/null 2>/dev/null <<EOF
   #include <cstdint>
   #include <nmmintrin.h>
   int main() {
@@ -565,13 +583,12 @@ $CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS -x c++ - -o /dev/null 2>/dev/null <<EOF
   }
 EOF
 if [ "$?" = 0 ]; then
-  COMMON_FLAGS="$COMMON_FLAGS -DHAVE_SSE42"
+  COMMON_FLAGS="$COMMON_FLAGS $TRY_SSE42 -DHAVE_SSE42"
 elif test "$USE_SSE"; then
   echo "warning: USE_SSE specified but compiler could not use SSE intrinsics, disabling" >&2
-  exit 1
 fi
 
-$CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS -x c++ - -o /dev/null 2>/dev/null <<EOF
+$CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS $TRY_PCLMUL -x c++ - -o /dev/null 2>/dev/null <<EOF
   #include <cstdint>
   #include <wmmintrin.h>
   int main() {
@@ -583,10 +600,9 @@ $CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS -x c++ - -o /dev/null 2>/dev/null <<EOF
   }
 EOF
 if [ "$?" = 0 ]; then
-  COMMON_FLAGS="$COMMON_FLAGS -DHAVE_PCLMUL"
+  COMMON_FLAGS="$COMMON_FLAGS $TRY_PCLMUL -DHAVE_PCLMUL"
 elif test "$USE_SSE"; then
   echo "warning: USE_SSE specified but compiler could not use PCLMUL intrinsics, disabling" >&2
-  exit 1
 fi
 
 # iOS doesn't support thread-local storage, but this check would erroneously
diff --git a/build_tools/fbcode_config.sh b/build_tools/fbcode_config.sh
index c2c39db48..4834be5f4 100644
--- a/build_tools/fbcode_config.sh
+++ b/build_tools/fbcode_config.sh
@@ -86,9 +86,10 @@ else
 fi
 CFLAGS+=" -DTBB"
 
-# use Intel SSE support for checksum calculations
-export USE_SSE=1
-export PORTABLE=1
+test "$USE_SSE" || USE_SSE=1
+export USE_SSE
+test "$PORTABLE" || PORTABLE=1
+export PORTABLE
 
 BINUTILS="$BINUTILS_BASE/bin"
 AR="$BINUTILS/ar"
diff --git a/build_tools/fbcode_config4.8.1.sh b/build_tools/fbcode_config4.8.1.sh
index 80fbdf431..5f0813a04 100644
--- a/build_tools/fbcode_config4.8.1.sh
+++ b/build_tools/fbcode_config4.8.1.sh
@@ -53,9 +53,10 @@ LIBUNWIND="$LIBUNWIND_BASE/lib/libunwind.a"
 TBB_INCLUDE=" -isystem $TBB_BASE/include/"
 TBB_LIBS="$TBB_BASE/lib/libtbb.a"
 
-# use Intel SSE support for checksum calculations
-export USE_SSE=1
-export PORTABLE=1
+test "$USE_SSE" || USE_SSE=1
+export USE_SSE
+test "$PORTABLE" || PORTABLE=1
+export PORTABLE
 
 BINUTILS="$BINUTILS_BASE/bin"
 AR="$BINUTILS/ar"
diff --git a/build_tools/fbcode_config_platform007.sh b/build_tools/fbcode_config_platform007.sh
index 9da23fd84..51edf134f 100644
--- a/build_tools/fbcode_config_platform007.sh
+++ b/build_tools/fbcode_config_platform007.sh
@@ -86,9 +86,10 @@ else
 fi
 CFLAGS+=" -DTBB"
 
-# use Intel SSE support for checksum calculations
-export USE_SSE=1
-export PORTABLE=1
+test "$USE_SSE" || USE_SSE=1
+export USE_SSE
+test "$PORTABLE" || PORTABLE=1
+export PORTABLE
 
 BINUTILS="$BINUTILS_BASE/bin"
 AR="$BINUTILS/ar"