Disable pthread for standalone wasm build support (#721) * Disable pthread for wasm build support * wasm -> wasm32

diff --git a/absl/BUILD.bazel b/absl/BUILD.bazel
index f7fc2a7..e45d15a 100644
--- a/absl/BUILD.bazel
+++ b/absl/BUILD.bazel

@@ -58,3 +58,8 @@
     },
     visibility = [":__subpackages__"],
 )
+
+config_setting(
+    name = "wasm",
+    values = {"cpu": "wasm32"},
+)

diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 745a598..23f2763 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel

@@ -161,6 +161,7 @@
     copts = ABSL_DEFAULT_COPTS,
     linkopts = select({
         "//absl:windows": [],
+        "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
     visibility = [
@@ -222,6 +223,7 @@
         "//absl:windows": [
             "-DEFAULTLIB:advapi32.lib",
         ],
+        "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
     deps = [

diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index d336246..bdc50e0 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel

@@ -148,6 +148,7 @@
     copts = ABSL_TEST_COPTS,
     linkopts = select({
         "//absl:windows": [],
+        "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
     deps = [

diff --git a/absl/random/internal/BUILD.bazel b/absl/random/internal/BUILD.bazel
index a0eba5e..83843b4 100644
--- a/absl/random/internal/BUILD.bazel
+++ b/absl/random/internal/BUILD.bazel

@@ -99,6 +99,7 @@
     copts = ABSL_DEFAULT_COPTS,
     linkopts = select({
         "//absl:windows": [],
+        "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
     deps = [

diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index 3f876b9..2cd5ae2 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel

@@ -90,6 +90,7 @@
     copts = ABSL_DEFAULT_COPTS,
     linkopts = select({
         "//absl:windows": [],
+        "//absl:wasm": [],
         "//conditions:default": ["-pthread"],
     }) + ABSL_DEFAULT_LINKOPTS,
     deps = [