Add target to build the Abseil C++ library.

Note that at this time support of the library is considered
unstable and we disable -Werror for cheri-capability-misuse.

pycheribuild/projects/cross/abseil.py

@@ -0,0 +1,43 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2023 Alfredo Mazzinghi
+#
+# This software was developed by SRI International, the University of
+# Cambridge Computer Laboratory (Department of Computer Science and
+# Technology), and Capabilities Limited under Defense Advanced Research
+# Projects Agency (DARPA) Contract No. HR001122S0003 ("MTSS").
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+from .crosscompileproject import CrossCompileCMakeProject, GitRepository
+
+
+class BuildAbseil(CrossCompileCMakeProject):
+    target = "abseil"
+    repository = GitRepository("https://github.com/CTSRD-CHERI/abseil-cpp.git",
+                               default_branch="cheri-20220623.0")
+
+    def setup(self):
+        super().setup()
+        # FIXME: The ElfMemImage in abseil is unported.
+        self.cross_warning_flags.append("-Wno-error=cheri-capability-misuse")