diff --git a/build/gen.py b/build/gen.py
index 76f88e84..5e088b2a 100755
--- a/build/gen.py
+++ b/build/gen.py
@@ -326,9 +326,6 @@ def WriteGNNinja(path, platform, host, options, linux_sysroot):
     if options.debug:
       cflags.extend(['-O0', '-g'])
     else:
-      cflags.append('-DNDEBUG')
-      cflags.append('-O3')
-      ldflags.append('-O3')
       # Use -fdata-sections and -ffunction-sections to place each function
       # or data item into its own section so --gc-sections can eliminate any
       # unused functions and data items.
@@ -340,14 +337,6 @@ def WriteGNNinja(path, platform, host, options, linux_sysroot):
         # Garbage collection is done by default on aix.
         ldflags.append('-Wl,--gc-sections')
 
-      # Omit all symbol information from the output file.
-      if platform.is_darwin():
-        ldflags.append('-Wl,-S')
-      elif platform.is_aix():
-        ldflags.append('-Wl,-s')
-      else:
-        ldflags.append('-Wl,-strip-all')
-
       # Enable identical code-folding.
       if options.use_icf:
         ldflags.append('-Wl,--icf=all')
@@ -356,26 +345,17 @@ def WriteGNNinja(path, platform, host, options, linux_sysroot):
         '-D_FILE_OFFSET_BITS=64',
         '-D__STDC_CONSTANT_MACROS', '-D__STDC_FORMAT_MACROS',
         '-pthread',
-        '-pipe',
         '-fno-exceptions',
         '-fno-rtti',
     ])
     cflags_cc.extend(['-std=c++14', '-Wno-c++11-narrowing'])
+    ldflags.append('-pthread')
 
     if platform.is_linux():
       if linux_sysroot:
         # Use the sid sysroot that UpdateLinuxSysroot() downloads.
         cflags.append('--sysroot=' + linux_sysroot)
         ldflags.append('--sysroot=' + linux_sysroot)
-      ldflags.extend([
-          '-static-libstdc++',
-          '-Wl,--as-needed',
-      ])
-      libs.extend([
-          # These are needed by libc++.
-          '-ldl',
-          '-lpthread',
-      ])
     elif platform.is_darwin():
       min_mac_version_flag = '-mmacosx-version-min=10.9'
       cflags.append(min_mac_version_flag)