[SCons] Fix regression causing unnecessary rebuilds.

The num_jobs (-j flag) was being tracked as part of the cmake and
openssl build actions, thus causing a rebuild when compiling with
different concurrently.

This commit strip the -j flag from the signature of the actions so
scons won't rebuild openssl/libdatachannel when changing the parallelism
option.

3 files changed, 23 insertions, 15 deletions

diff --git a/tools/cmake.py b/tools/cmake.py
index 28e1269..4141ee0 100644
--- a/tools/cmake.py
+++ b/tools/cmake.py
@@ -87,9 +87,13 @@ def cmake_emitter(target, source, env):
     return [str(target[0]) + "/CMakeCache.txt"] + target[1:], [str(source[0]) + "/CMakeLists.txt"] + source[1:]
 
 
-cmake_configure_action = SCons.Action.Action("$CMAKECONFCOM", "$CMAKECONFCOMSTR")
-cmake_build_action = SCons.Action.Action("$CMAKEBUILDCOM", "$CMAKEBUILDCOMSTR")
-cmake_builder = SCons.Builder.Builder(action=[cmake_configure_action, cmake_build_action], emitter=cmake_emitter)
+def cmake_generator(target, source, env, for_signature):
+    # Strip the -j option for signature to avoid rebuilding when num_jobs changes.
+    build = env["CMAKEBUILDCOM"].replace("-j$CMAKEBUILDJOBS", "") if for_signature else env["CMAKEBUILDCOM"]
+    return [
+        SCons.Action.Action("$CMAKECONFCOM", "$CMAKECONFCOMSTR"),
+        SCons.Action.Action(build, "$CMAKEBUILDCOMSTR"),
+    ]
 
 
 def exists(env):
@@ -104,6 +108,7 @@ def generate(env):
     env["CMAKEGENERATOR"] = ""
     env["CMAKECONFFLAGS"] = SCons.Util.CLVar("")
     env["CMAKECONFCOM"] = "$CMAKE -B ${TARGET.dir} $CMAKEPLATFORMCONFIG $CMAKECONFFLAGS ${SOURCE.dir}"
+    env["CMAKEBUILDJOBS"] = "${__env__.GetOption('num_jobs')}"
     env["CMAKEBUILDFLAGS"] = SCons.Util.CLVar("")
-    env["CMAKEBUILDCOM"] = "$CMAKE --build ${TARGET.dir} $CMAKEBUILDFLAGS"
-    env["BUILDERS"]["CMake"] = cmake_builder
+    env["CMAKEBUILDCOM"] = "$CMAKE --build ${TARGET.dir} $CMAKEBUILDFLAGS -j$CMAKEBUILDJOBS"
+    env["BUILDERS"]["CMake"] = SCons.Builder.Builder(generator=cmake_generator, emitter=cmake_emitter)
diff --git a/tools/openssl.py b/tools/openssl.py
index 936895d..8af782a 100644
--- a/tools/openssl.py
+++ b/tools/openssl.py
@@ -144,6 +144,17 @@ def build_openssl(env, jobs=None):
     return ssl
 
 
+def ssl_generator(target, source, env, for_signature):
+    # Strip the -j option for signature to avoid rebuilding when num_jobs changes.
+    build = env["SSLBUILDCOM"].replace("-j$SSLBUILDJOBS", "") if for_signature else env["SSLBUILDCOM"]
+    return [
+        Mkdir("$SSL_BUILD"),
+        Mkdir("$SSL_INSTALL"),
+        SCons.Action.Action("$SSLCONFIGCOM", "$SSLCONFIGCOMSTR"),
+        SCons.Action.Action(build, "$SSLBUILDCOMSTR"),
+    ]
+
+
 def options(opts):
     opts.Add(PathVariable("openssl_source", "Path to the openssl sources.", "thirdparty/openssl"))
     opts.Add("openssl_build", "Destination path of the openssl build.", "bin/thirdparty/openssl")
@@ -194,13 +205,5 @@ def generate(env):
     if env["platform"] == "windows" and env.get("is_msvc", False):
         env["SSLBUILDCOM"] = "cd ${TARGET.dir} && nmake install_sw install_ssldirs"
 
-    env["BUILDERS"]["OpenSSLBuilder"] = SCons.Builder.Builder(
-        action=[
-            Mkdir("$SSL_BUILD"),
-            Mkdir("$SSL_INSTALL"),
-            SCons.Action.Action("$SSLCONFIGCOM", "$SSLCONFIGCOMSTR"),
-            SCons.Action.Action("$SSLBUILDCOM", "$SSLBUILDCOMSTR"),
-        ],
-        emitter=ssl_emitter,
-    )
+    env["BUILDERS"]["OpenSSLBuilder"] = SCons.Builder.Builder(generator=ssl_generator, emitter=ssl_emitter)
     env.AddMethod(build_openssl, "OpenSSL")
diff --git a/tools/rtc.py b/tools/rtc.py
index 798dc94..61b6bcc 100644
--- a/tools/rtc.py
+++ b/tools/rtc.py
@@ -27,7 +27,7 @@ def build_library(env):
     rtc_targets = [env.Dir(env["RTC_BUILD"])] + env["RTC_LIBS"]
     rtc_sources = [env.Dir(env["RTC_SOURCE"])]
     rtc_env.Append(CMAKECONFFLAGS=["'-D%s=%s'" % it for it in rtc_cmake_config(env).items()])
-    rtc_env.Append(CMAKEBUILDFLAGS=["-t", "datachannel-static", "-j%s" % env.GetOption("num_jobs")])
+    rtc_env.Append(CMAKEBUILDFLAGS=["-t", "datachannel-static"])
     rtc = rtc_env.CMake(rtc_targets, rtc_sources, CMAKEBUILDTYPE=env["RTC_BUILD_TYPE"])
     rtc_env.Depends(rtc, rtc_env["SSL_LIBS"])
     return rtc