auto/otel: Fix breakage on non-Linux platforms

[ac000]

auto/otel: Fix breakage on non-Linux platforms

When building with --otel on macOS for example I was seeing compile
failures with the cpu_set_t stuff which should only be used under Linux.

It turned out that despite

  checking for Linux sched_getaffinity() ... not found

we were getting

  #ifndef NXT_HAVE_LINUX_SCHED_GETAFFINITY
  #define NXT_HAVE_LINUX_SCHED_GETAFFINITY  1
  #endif

in build/include/nxt_auto_config.h

It seems this was due to the

    . auto/feature

in auto/otel, this check happens right after the above. Without having

    nxt_feature_name=NXT_HAVE_OTEL

set.

Instead we were adding the define for that manually.

Doing auto/feature without having a nxt_feature_name must have used the
last set one and enabled it.

Set nxt_feature_name and remove the manual editing of nxt_auto_config.h

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

[thresheek]

This patch seems correct to address this particular issue.

My fix for macOS build uses a similar trick, but we also need to link with additional frameworks on that OS: thresheek@660e853

Also, another fix is required to be able to build on macOS: thresheek@18381b1

We probably want to incorporate those changes in this PR for the sake of completeness.

[ac000]

This patch seems correct to address this particular issue.

It would affect any system that didn't have a Linux compatible sched_getaffinity(2), not that I was aware of any that did, but it seems at least FreeBSD does, so I'll need to tweak the commit subject...

My fix for macOS build uses a similar trick, but we also need to link with additional frameworks on that OS: thresheek@660e853

Weird, I wonder what is doing that... it certainly uses regular OpenSSL for general TLS support...

Also, another fix is required to be able to build on macOS: thresheek@18381b1

This one makes sense.

We probably want to incorporate those changes in this PR for the sake of completeness.

But then there is some other breakage also with --otel

(in auto/make)

 87 ifeq (\$D,1)
 88         NXT_OTEL_LIB_LOC = $NXT_OTEL_LIB_DIR/target/debug/libotel.a
 89 else
 90         NXT_OTEL_LIB_LOC = $NXT_OTEL_LIB_DIR/target/release/libotel.a
 91 endif

Prevents the use of make on at least FreeBSD, however, it also breaks with gmake as D has not been set as that only happens when

 44 if [ -n "$NXT_GNU_MAKE" ] || [ $NXT_OS = "SunOS" ]; then

And then above that we have

 64 ifeq (\$D,1)                                                                
 65         CFLAGS += -O0                                                       
 66         RUST_FLAGS += --debug                                               
 67 else                                                                        
 68         RUST_FLAGS += --release                                             
 69 endif

However that is guarded by the

 44 if [ -n "$NXT_GNU_MAKE" ] || [ $NXT_OS = "SunOS" ]; then                 

So on the likes of FreeBSD RUST_FLAGS isn't set all...

I don't mind making GNU make a build dependency... however at the moment it seems --otel is fubar on anything non-Linux... (between needing sched_getaffinity(2) and GNU make being the default make(1))

[ac000]

Some of this would be simpler if we could just tell rustc to write the library to build/lib/libotel.a, oh right, we can...

cargo build ... --emit link=../../build/lib/libotel.a

and then just do debug builds by default and enable release builds by setting a cargo environment variable, but that seems to be a stumbling block as unless I missed it, that seems to be the one thing you can't set...

[ac000]

While we're at it could we

s/NXT_OTEL_LIB_LOC/NXT_OTEL_LIB_STATIC