[PATCH] selftest: alsa: check if user has alsa installed

[Abdul Rahim <abdul.rahim@xxxxxxxxxxx>]

Currently, if alsa development package is not installed on the user's
system then the make command would print a `pagefull` of errors. In
particular one error message is repeated 3 times. This error is returned
by `pkg-config` and since it is not being handeled appropriately,
repeated calls to `pkg-config` prints the same message again.

This patch adds check for alsa package installation. If alsa is not
installed, a short and consize error is returned. Also, it does not
affect the compilation of other tests.

Signed-off-by: Abdul Rahim <abdul.rahim@xxxxxxxxxxx>
---

Current output:
```
make[3]: Entering directory '/mnt/ubuntu/abdul_linux/mainline_dev/tools/testing/selftests/alsa'
Makefile:4: *** Package alsa not found, please install alsa development package or add directory containing `alsa.pc` in PKG_CONFIG_PATH.  Stop.
make[3]: Leaving directory '/mnt/ubuntu/abdul_linux/mainline_dev/tools/testing/selftests/alsa'
make[3]: Entering directory '/mnt/ubuntu/abdul_linux/mainline_dev/tools/testing/selftests/amd-pstate'
```

Previous output:
```
make[3]: Entering directory '/mnt/ubuntu/abdul_linux/mainline_compile/tools/testing/selftests/alsa'
Package alsa was not found in the pkg-config search path.
Perhaps you should add the directory containing `alsa.pc'
to the PKG_CONFIG_PATH environment variable
Package 'alsa', required by 'virtual:world', not found
Package alsa was not found in the pkg-config search path.
Perhaps you should add the directory containing `alsa.pc'
to the PKG_CONFIG_PATH environment variable
Package 'alsa', required by 'virtual:world', not found
Package alsa was not found in the pkg-config search path.
Perhaps you should add the directory containing `alsa.pc'
to the PKG_CONFIG_PATH environment variable
Package 'alsa', required by 'virtual:world', not found
gcc  -isystem /mnt/ubuntu/abdul_linux/mainline_compile/usr/include -L/mnt/ubuntu/abdul_linux/mainline_compile/tools/testing/selftests/alsa       -Wl,-rpath=./ -D_GNU_SOURCE=  -shared -fPIC conf.c  -lasound -lpthread -o /mnt/ubuntu/abdul_linux/mainline_compile/tools/testing/selftests/      alsa/libatest.so
In file included from conf.c:18:
alsa-local.h:11:10: fatal error: alsa/asoundlib.h: No such file or directory
   11 | #include <alsa/asoundlib.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
make[3]: *** [Makefile:24: /mnt/ubuntu/abdul_linux/mainline_compile/tools/testing/selftests/alsa/libatest.so] Error 1
```

 tools/testing/selftests/alsa/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/alsa/Makefile b/tools/testing/selftests/alsa/Makefile
index 25be68025290..944279160fed 100644
--- a/tools/testing/selftests/alsa/Makefile
+++ b/tools/testing/selftests/alsa/Makefile
@@ -1,5 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
 #
+ifneq ($(shell pkg-config --exists alsa && echo 0 || echo 1),0)
+$(error Package alsa not found, please install alsa development package or \
+	add directory containing `alsa.pc` in PKG_CONFIG_PATH)
+endif
 
 CFLAGS += $(shell pkg-config --cflags alsa) $(KHDR_INCLUDES)
 LDLIBS += $(shell pkg-config --libs alsa)
-- 
2.46.0