Issues building latest Apple Swift 5 master branch on PowerPC64LE

Facing the following issue while building the latest Apple Swift master branch(GitHub - apple/swift: The Swift Programming Language) on PowerPC64LE

[2431/3406][ 71%][1250.949s] Building CXX object tools/clang/lib/DirectoryWatcher/CMakeFiles/clangDirectoryWatcher.dir/DirectoryWatcher.cpp.o
FAILED: tools/clang/lib/DirectoryWatcher/CMakeFiles/clangDirectoryWatcher.dir/DirectoryWatcher.cpp.o
/usr/bin/clang++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools/clang/lib/DirectoryWatcher -I/home/sar/swift-source/llvm/tools/clang/lib/DirectoryWatcher -I/home/sar/swift-source/llvm/tools/clang/include -Itools/clang/include -I/usr/include/libxml2 -Iinclude -I/home/sar/swift-source/llvm/include -Wno-unknown-warning-option -Werror=unguarded-availability-new -fno-stack-protector -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -std=c++11 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wcovered-switch-default -Wno-class-memaccess -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -fdiagnostics-color -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -Wno-nested-anon-types -O3 -UNDEBUG -fno-exceptions -fno-rtti -MMD -MT tools/clang/lib/DirectoryWatcher/CMakeFiles/clangDirectoryWatcher.dir/DirectoryWatcher.cpp.o -MF tools/clang/lib/DirectoryWatcher/CMakeFiles/clangDirectoryWatcher.dir/DirectoryWatcher.cpp.o.d -o tools/clang/lib/DirectoryWatcher/CMakeFiles/clangDirectoryWatcher.dir/DirectoryWatcher.cpp.o -c /home/sar/swift-source/llvm/tools/clang/lib/DirectoryWatcher/DirectoryWatcher.cpp
In file included from /home/sar/swift-source/llvm/tools/clang/lib/DirectoryWatcher/DirectoryWatcher.cpp:98:
/home/sar/swift-source/llvm/tools/clang/lib/DirectoryWatcher/DirectoryWatcher-linux.inc.h:95:23: error: use of undeclared identifier 'RetryAfterSignal'
ssize_t numRead = RetryAfterSignal(-1, read, inotifyFD, buf, EventBufferLength);
^
/home/sar/swift-source/llvm/tools/clang/lib/DirectoryWatcher/DirectoryWatcher-linux.inc.h:100:36: error: 'char' is not a class
struct inotify_event *ievt = dynamic_cast<struct inotify_event *>(p);
^ ~
/home/sar/swift-source/llvm/tools/clang/lib/DirectoryWatcher/DirectoryWatcher-linux.inc.h:181:3: error: use of undeclared identifier 'RetryAfterSignal'; did you mean 'llvm::sys::RetryAfterSignal'?
RetryAfterSignal(-1, close, inotifyFD);
^~~~~~~~~~~~~~~~
llvm::sys::RetryAfterSignal
/home/sar/swift-source/llvm/include/llvm/Support/Errno.h:34:13: note: 'llvm::sys::RetryAfterSignal' declared here
inline auto RetryAfterSignal(const FailT &Fail, const Fun &F,
^
3 errors generated.
[2432/3406][ 71%][1250.950s] Building CXX object tools/clang/lib/Tooling/Refactoring/CMakeFiles/clangToolingRefactoring.dir/Rename/RenamingAction.cpp.o
[2433/3406][ 71%][1251.875s] Building CXX object tools/clang/lib/Tooling/Refactor/CMakeFiles/clangToolingRefactor.dir/USRFinder.cpp.o
[2434/3406][ 71%][1264.030s] Building CXX object tools/clang/lib/Tooling/Refactoring/CMakeFiles/clangToolingRefactoring.dir/Rename/USRFindingAction.cpp.o
[2435/3406][ 71%][1264.794s] Building CXX object tools/clang/lib/Tooling/ASTDiff/CMakeFiles/clangToolingASTDiff.dir/ASTDiff.cpp.o
[2436/3406][ 71%][1268.950s] Building CXX object tools/clang/lib/Tooling/Refactoring/CMakeFiles/clangToolingRefactoring.dir/Rename/USRFinder.cpp.o
[2437/3406][ 71%][1270.868s] Building CXX object tools/clang/lib/Tooling/Refactoring/CMakeFiles/clangToolingRefactoring.dir/Rename/USRLocFinder.cpp.o
[2438/3406][ 71%][1305.238s] Building CXX object tools/clang/lib/Tooling/Refactor/CMakeFiles/clangToolingRefactor.dir/Extract.cpp.o
ninja: build stopped: subcommand failed.
Building the standard library for: swift-stdlib-linux-powerpc64le
Running Swift tests for: check-swift-all-linux-powerpc64le check-swift-all-optimize-linux-powerpc64le
./utils/build-script: fatal error: command terminated with a non-zero exit status 1, aborting
./utils/build-script: fatal error: command terminated with a non-zero exit status 1, aborting
sar@267538d18c75:~$

Looks like the master is currently failing to build on every platform except for macOS at the moment.
All with exactly the same error as you are reporting.