Description:

When I was trying to run PipeWire with a filter chain that has a LADSPA node with a Low Pass filter the service failed to start. Searching through the logs it shows that a no such file or directory error happened, so I've run `listplugins` to see if the filter plugin, `filter.so`, was indeed listed but to my surprise it didn't appear. Listing its details with `analyseplugin filter.so` worked as expected, so I started to suspect that a link to a library was missing. Then I've listed its dynamic symbols with `nm -D -u` and in the output it had two symbols, `sqrtf` and `cos`, both members of libm which made me realize that it was missing and indeed, `ldd` confirms this.

```
$ LD_WARN=1 ldd -r /usr/lib/ladspa/filter.so
linux-vdso.so.1 (0x00007ffe0e9c9000)
libc.so.6 => /usr/lib/libc.so.6 (0x00007fb7f420a000)
/usr/lib64/ld-linux-x86-64.so.2 (0x00007fb7f444c000)
undefined symbol: sqrtf (/usr/lib/ladspa/filter.so)
undefined symbol: cos (/usr/lib/ladspa/filter.so)
```

So to fix the issue I've used the following patch.

```patch
--- a/src/Makefile
+++ b/src/Makefile
@@ -41,6 +41,7 @@ CPP = c++
plugins/$*.o \
-shared \
$(CFLAGS) \
+ -lm \
-fvisibility=hidden \
-fvisibility-inlines-hidden \
-s \
@@ -52,6 +53,7 @@ CPP = c++
plugins/$*.o \
-shared \
$(CXXFLAGS) \
+ -lm \
-fvisibility=hidden \
-fvisibility-inlines-hidden \
-s \
```

Additional info:
* package version(s): ladspa 1.17

Steps to reproduce:

1. Use this config for PipeWire.

```
context.modules = [
{ name = libpipewire-module-filter-chain
args = {
node.description = "Noise Canceling sink"
media.name = "Noise Canceling sink"
filter.graph = {
nodes = [
{
type = ladspa
name = lopassL
plugin = /usr/lib/ladspa/filter.so
label = lpf
control = {
"Cutoff Frequency (Hz)" 440
}
}
{
type = ladspa
name = lopassR
plugin = /usr/lib/ladspa/filter.so
label = lpf
control = {
"Cutoff Frequency (Hz)" 440
}
}
]
inputs = [ "lopassL:Input" "lopassR:Input" ]
outputs = [ "lopassL:Output" "lopassR:Output" ]
}
capture.props = {
node.name = "effect_output.rnnoise"
media.class = Audio/Sink
audio.channels = 2
audio.position = [ FL FR ]
audio.rate = 48000
}
playback.props = {
node.name = "effect_input.rnnoise"
node.passive = true
audio.channels = 2
audio.position = [ FL FR ]
audio.rate = 48000
}
}
}
]
```

2. List plugins with `listplugins` or try to autocomplete `analyseplugin` and see that `filter` is not available.

3. Show the symbols of `/usr/lib/ladspa/filter.so` with `nm -D -u` and list its rundeps with `LD_WARN=1 ldd -r /usr/lib/ladspa/filter.so`.